Fibrous elements comprising a non-hydroxyl polymer and methods for making same

ABSTRACT

Fibrous elements, such as filaments and/or fibers, and more particularly to fibrous elements that contain a non-hydroxyl polymer, fibrous structures made therefrom, and methods for making same are provided.

FIELD OF THE INVENTION

The present invention relates to fibrous elements, such as filamentsand/or fibers, and more particularly to fibrous elements that comprise anon-hydroxyl polymer, fibrous structures made therefrom, and methods formaking same.

BACKGROUND OF THE INVENTION

Fibrous elements, especially produced from spinning processes such asmeltblow and/or spunbond processes are known in the art. For example,fibrous elements comprising a fibrous element-forming polymer, such as ahydroxyl polymer, and a non-hydroxyl polymer, such as a polyacrylamide,that exhibits a weight average molecular weight of 1,320,000 g/mol orless are known in the art. Further, fibrous elements comprising afibrous element-forming polymer, such as a hydroxyl polymer, and anon-hydroxyl polymer, such as a polyacrylamide, that exhibit apolydispersity of 1.31 or less are known in the art. Further, fibrouselements comprising a fibrous element-forming polymer, such as ahydroxyl polymer, and a non-hydroxyl polymer, such as a polyacrylamide,wherein the non-hydroxyl polymer is present in the fibrous element at aconcentration less than its entanglement concentration (Ce).

However, such fibrous elements and fibrous structures comprising suchknown fibrous elements exhibit lower than desired strength properties,such as lower than desired dry tensile properties including lower thandesired fail total energy absorption properties.

As shown above, a problem encountered by formulators is how to improvethe dry tensile properties of 1) fibrous elements comprising a fibrouselement-forming polymer, such as a hydroxyl polymer, and a non-hydroxylpolymer, such as polyacrylamide, and 2) fibrous structures comprisingsuch fibrous elements.

Therefore, there is a need for fibrous elements produced from polymermelt compositions comprising a fibrous element-forming polymer and anon-hydroxyl polymer and fibrous structures made therefrom that avoidthe negatives discussed above.

SUMMARY OF THE INVENTION

The present invention fulfills the need described above by providing afibrous element comprising a non-hydroxyl polymer, such as apolyacrylamide, that exhibits improved dry tensile properties, a fibrousstructure formed therefrom, and a method for making such a fibrouselement and/or fibrous structure.

A solution to the problem identified above is to incorporate anon-hydroxyl polymer into an aqueous polymer melt composition to producefibrous elements such that the fibrous element comprise the non-hydroxylpolymer having a weight average molecular weight of greater than1,400,000 g/mol and/or having a polydispersity of greater than 1.32.such that the fibrous elements and/or fibrous structures comprising suchfibrous elements exhibit improved dry tensile properties compared tofibrous elements comprising the non-hydroxyl polymer having a weightaverage molecular weight of less than 1,400,000 g/mol and/or having apolydispersity of 1.31 or less.

In one example of the present invention, a fibrous element comprising afibrous element-forming polymer, such as a hydroxyl polymer, and anon-hydroxyl polymer, wherein the non-hydroxyl polymer exhibits a weightaverage molecular weight of greater than 1,400,000 g/mol, is provided.

In another example of the present invention, a fibrous elementcomprising a fibrous element-forming polymer, such as a hydroxylpolymer, and a non-hydroxyl polymer, wherein the non-hydroxyl polymer ispresent in the fibrous element at a concentration that is greater thanits engtanglement concentration (C_(e)), is provided.

In another example of the present invention, a fibrous elementcomprising a fibrous element-forming polymer, such as a hydroxylpolymer, and a non-hydroxyl polymer, wherein the non-hydroxyl polymerexhibits a polydispersity of greater than 1.32, is provided.

In still another example of the present invention, a fibrous structurecomprising a plurality of fibrous elements of the present invention, isprovided.

In still another example of the present invention, an aqueous polymermelt composition comprising a fibrous element-forming polymer, such as ahydroxyl polymer, and a non-hydroxyl polymer that exhibits a weightaverage molecular weight of greater than 1,400,000 g/mol, is provided.

In still another example of the present invention, an aqueous polymermelt composition comprising a fibrous element-forming polymer, such as ahydroxyl polymer, and a non-hydroxyl polymer present in the aqueouspolymer melt composition at a concentration that is greater than itsengtanglement concentration (C_(e)), is provided.

In still another example of the present invention, an aqueous polymermelt composition comprising a fibrous element-forming polymer, such as ahydroxyl polymer, and a non-hydroxyl polymer that exhibits apolydispersity of greater than 1.32, is provided.

In yet another example of the present invention, a polymeric structure,such as a fibrous element, derived from an aqueous polymer meltcomposition of the present invention, is provided.

In still yet another example of the present invention, a method formaking a fibrous element of the present invention comprising the stepsof:

-   -   a. providing an aqueous polymer melt composition comprising a        fibrous element-forming polymer, such as a hydroxyl polymer, and        a non-hydroxyl polymer that exhibits a weight average molecular        weight of greater than 1,400,000 g/mol; and    -   b. polymer processing the aqueous polymer melt composition such        that one or more fibrous elements are formed, is provided.

In still yet another example of the present invention, a method formaking a fibrous element of the present invention comprising the stepsof:

-   -   a. providing an aqueous polymer melt composition comprising a        fibrous element-forming polymer, such as a hydroxyl polymer, and        a non-hydroxyl polymer, wherein the non-hydroxyl polymer is        present in the aqueous polymer melt composition at a        concentration that is greater than its engtanglement        concentration (C_(e)); and    -   b. polymer processing the aqueous polymer melt composition such        that one or more fibrous elements are formed, is provided.

In still yet another example of the present invention, a method formaking a fibrous element of the present invention comprising the stepsof:

-   -   a. providing an aqueous polymer melt composition comprising a        fibrous element-forming polymer, such as a hydroxyl polymer, and        a non-hydroxyl polymer that exhibits a polydispersity of greater        than 1.32; and    -   b. polymer processing the aqueous polymer melt composition such        that one or more fibrous elements are formed, is provided.

In even still yet another example of the present invention, a method formaking a polymeric structure of the present invention comprising thesteps of:

-   -   a. providing an aqueous polymer melt composition comprising a        fibrous element-forming polymer, such as a hydroxyl polymer, and        a non-hydroxyl polymer that exhibits a weight average molecular        weight of greater than 1,400,000 g/mol; and    -   b. polymer processing the aqueous polymer melt composition such        that one or more polymeric structures are formed, is provided.

In even still yet another example of the present invention, a method formaking a polymeric structure of the present invention comprising thesteps of:

-   -   a. providing an aqueous polymer melt composition comprising a        fibrous element-forming polymer, such as a hydroxyl polymer, and        a non-hydroxyl polymer, wherein the non-hydroxyl polymer is        present in the aqueous polymer melt composition at a        concentration that is greater than its engtanglement        concentration (C_(e)); and    -   b. polymer processing the aqueous polymer melt composition such        that one or more polymeric structures are formed, is provided.

In even still yet another example of the present invention, a method formaking a polymeric structure of the present invention comprising thesteps of:

-   -   a. providing an aqueous polymer melt composition comprising a        fibrous element-forming polymer, such as a hydroxyl polymer, and        a non-hydroxyl polymer that exhibits a polydispersity of greater        than 1.32; and    -   b. polymer processing the aqueous polymer melt composition such        that one or more polymeric structures are formed, is provided.

In even yet another example of the present invention, a method formaking a fibrous structure of the present invention comprising the stepsof:

-   -   a. providing an aqueous polymer melt composition comprising a        fibrous element-forming polymer, such as a hydroxyl polymer, and        a non-hydroxyl polymer that exhibits a weight average molecular        weight of greater than 1,400,000 g/mol;    -   b. polymer processing the aqueous polymer melt composition such        that a plurality of fibrous elements are formed; and    -   c. collecting the fibrous elements on a collection device such        that a fibrous structure is formed, is provided.

In even yet another example of the present invention, a method formaking a fibrous structure of the present invention comprising the stepsof:

-   -   a. providing an aqueous polymer melt composition comprising a        fibrous element-forming polymer, such as a hydroxyl polymer, and        a non-hydroxyl polymer, wherein the non-hydroxyl polymer is        present in the aqueous polymer melt composition at a        concentration that is greater than its engtanglement        concentration (C_(e));    -   b. polymer processing the aqueous polymer melt composition such        that a plurality of fibrous elements are formed; and    -   c. collecting the fibrous elements on a collection device such        that a fibrous structure is formed, is provided.

In even yet another example of the present invention, a method formaking a fibrous structure of the present invention comprising the stepsof:

-   -   a. providing an aqueous polymer melt composition comprising a        fibrous element-forming polymer, such as a hydroxyl polymer, and        a non-hydroxyl polymer that exhibits a polydispersity of greater        than 1.32;    -   b. polymer processing the aqueous polymer melt composition such        that a plurality of fibrous elements are formed; and    -   c. collecting the fibrous elements on a collection device such        that a fibrous structure is formed, is provided.

In even still another example of the present invention, a single- ormulti-ply sanitary tissue product comprising a fibrous structure of thepresent invention, is provided.

Accordingly, the present invention relates to polymeric structures, suchas fibrous elements, comprising a non-hydroxyl polymer, fibrousstructures made from such fibrous elements, and processes for makingsame.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of one example of a method formaking a fibrous structure according to the present invention;

FIG. 2 is a schematic representation of one example of a portion offibrous structure making process according to the present invention;

FIG. 3 is a schematic representation of an example of a meltblow die inaccordance with the present invention;

FIG. 4A is a schematic representation of an example of a barrel of atwin screw extruder in accordance with the present invention;

FIG. 4B is a schematic representation of an example of a screw andmixing element configuration for the twin screw extruder of FIG. 4A;

FIG. 5A is a schematic representation of an example of a barrel of atwin screw extruder suitable for use in the present invention;

FIG. 5B is a schematic representation of an example of a screw andmixing element configuration suitable for use in the barrel of FIG. 5A;

FIG. 6 is a schematic representation of an example of a process forsynthesizing a fibrous element in accordance with the present invention;

FIG. 7 is a schematic representation of a partial side view of theprocess shown in FIG. 6 showing an example of an attenuation zone;

FIG. 8 is a schematic plan view taken along lines 8-8 of FIG. 7 andshowing one possible arrangement of a plurality of extrusion nozzlesarranged to provide fibrous elements of the present invention;

FIG. 9 is a view similar to that of FIG. 8 and showing one possiblearrangement of orifices for providing a boundary air around theattenuation zone shown in FIG. 7 ; and

FIG. 10 is a plot of Weight Average Molecular Weight (MW) toPolydispersity (Mw/MN) for non-hydroxyl polymers.

DETAILED DESCRIPTION OF THE INVENTION Definitions

“Fibrous structure” as used herein means a structure that comprises oneor more fibrous elements. In one example, a fibrous structure accordingto the present invention means an association of fibrous elements thattogether form a structure capable of performing a function.

Non-limiting examples of processes for making fibrous structures includeknown wet-laid papermaking processes, air-laid papermaking processes,and wet, solution, and dry filament spinning processes, for examplemeltblowing and spunbonding spinning processes that are typicallyreferred to as nonwoven processes. Further processing of the formedfibrous structure may be carried out such that a finished fibrousstructure is formed. For example, in typical papermaking processes, thefinished fibrous structure is the fibrous structure that is wound on thereel at the end of papermaking. The finished fibrous structure maysubsequently be converted into a finished product, e.g. a sanitarytissue product.

“Fibrous element” as used herein means an elongate particulate having alength greatly exceeding its average diameter, i.e. a length to averagediameter ratio of at least about 10. A fibrous element may be a filamentor a fiber. In one example, the fibrous element is a single fibrouselement rather than a yarn comprising a plurality of fibrous elements.

The fibrous elements of the present invention may be spun from polymermelt compositions via suitable spinning operations, such as meltblowingand/or spunbonding and/or they may be obtained from natural sources suchas vegetative sources, for example trees.

The fibrous elements of the present invention may be monocomponentand/or multicomponent. For example, the fibrous elements may comprisebicomponent fibers and/or filaments. The bicomponent fibers and/orfilaments may be in any form, such as side-by-side, core and sheath,islands-in-the-sea and the like.

“Filament” as used herein means an elongate particulate as describedabove that exhibits a length of greater than or equal to 5.08 cm (2 in.)and/or greater than or equal to 7.62 cm (3 in.) and/or greater than orequal to 10.16 cm (4 in.) and/or greater than or equal to 15.24 cm (6in.).

Filaments are typically considered continuous or substantiallycontinuous in nature. Filaments are relatively longer than fibers.Non-limiting examples of filaments include meltblown and/or spunbondfilaments. Non-limiting examples of polymers that can be spun intofilaments include natural polymers, such as starch, starch derivatives,cellulose, such as rayon and/or lyocell, and cellulose derivatives,hemicellulose, hemicellulose derivatives, and synthetic polymersincluding, but not limited to polyvinyl alcohol, thermoplastic polymer,such as polyesters, nylons, polyolefins such as polypropylene filaments,polyethylene filaments, and biodegradable thermoplastic fibers such aspolylactic acid filaments, polyhydroxyalkanoate filaments,polyesteramide filaments and polycaprolactone filaments.

“Fiber” as used herein means an elongate particulate as described abovethat exhibits a length of less than 5.08 cm (2 in.) and/or less than3.81 cm (1.5 in.) and/or less than 2.54 cm (1 in.).

Fibers are typically considered discontinuous in nature. Non-limitingexamples of fibers include pulp fibers, such as wood pulp fibers, andsynthetic staple fibers such as polypropylene, polyethylene, polyester,copolymers thereof, rayon, glass fibers and polyvinyl alcohol fibers.

Staple fibers may be produced by spinning a filament tow and thencutting the tow into segments of less than 5.08 cm (2 in.) thusproducing fibers.

In one example of the present invention, a fiber may be a naturallyoccurring fiber, which means it is obtained from a naturally occurringsource, such as a vegetative source, for example a tree and/or plant.Such fibers are typically used in papermaking and are oftentimesreferred to as papermaking fibers. Papermaking fibers useful in thepresent invention include cellulosic fibers commonly known as wood pulpfibers. Applicable wood pulps include chemical pulps, such as Kraft,sulfite, and sulfate pulps, as well as mechanical pulps including, forexample, groundwood, thermomechanical pulp and chemically modifiedthermomechanical pulp. Chemical pulps, however, may be preferred sincethey impart a superior tactile sense of softness to fibrous structuresmade therefrom. Pulps derived from both deciduous trees (hereinafter,also referred to as “hardwood”) and coniferous trees (hereinafter, alsoreferred to as “softwood”) may be utilized. The hardwood and softwoodfibers can be blended, or alternatively, can be deposited in layers toprovide a stratified web. Also applicable to the present invention arefibers derived from recycled paper, which may contain any or all of theabove categories of fibers as well as other non-fibrous polymers such asfillers, softening agents, wet and dry strength agents, and adhesivesused to facilitate the original papermaking.

In addition to the various wood pulp fibers, other cellulosic fiberssuch as cotton linters, rayon, lyocell, and bagasse fibers can be usedin the fibrous structures of the present invention.

“Sanitary tissue product” as used herein means a soft, relatively lowdensity fibrous structure useful as a wiping implement for post-urinaryand post-bowel movement cleaning (toilet tissue), forotorhinolaryngological discharges (facial tissue), multi-functionalabsorbent and cleaning uses (absorbent towels) and wipes, such as wetand dry wipes. The sanitary tissue product may be convolutedly woundupon itself about a core or without a core to form a sanitary tissueproduct roll or may be in the form of discrete sheets.

In one example, the sanitary tissue product of the present inventioncomprises one or more fibrous structures according to the presentinvention. The fibrous structure and/or sanitary tissue products may beembossed.

The sanitary tissue products and/or fibrous structures of the presentinvention may exhibit a basis weight between about 10 g/m² to about 120g/m² and/or from about 15 g/m² to about 110 g/m² and/or from about 20g/m² to about 100 g/m² and/or from about 30 to 90 g/m² as determined bythe Basis Weight Test Method described herein. In addition, the sanitarytissue product of the present invention may exhibit a basis weightbetween about 40 g/m² to about 120 g/m² and/or from about 50 g/m² toabout 110 g/m² and/or from about 55 g/m² to about 105 g/m² and/or fromabout 60 g/m² to 100 g/m² as determined by the Basis Weight Test Methoddescribed herein.

The sanitary tissue products of the present invention may exhibit atotal dry tensile strength of greater than about 59 g/cm (150 g/in)and/or from about 78 g/cm (200 g/in) to about 394 g/cm (1000 g/in)and/or from about 98 g/cm (250 g/in) to about 335 g/cm (850 g/in). Inaddition, the sanitary tissue product of the present invention mayexhibit a total dry tensile strength of greater than about 196 g/cm (500g/in) and/or from about 196 g/cm (500 g/in) to about 394 g/cm (1000g/in) and/or from about 216 g/cm (550 g/in) to about 335 g/cm (850 g/in)and/or from about 236 g/cm (600 g/in) to about 315 g/cm (800 g/in). Inone example, the sanitary tissue product exhibits a total dry tensilestrength of less than about 394 g/cm (1000 g/in) and/or less than about335 g/cm (850 g/in).

The sanitary tissue products of the present invention may exhibit aninitial total wet tensile strength of less than about 78 g/cm (200 g/in)and/or less than about 59 g/cm (150 g/in) and/or less than about 39 g/cm(100 g/in) and/or less than about 29 g/cm (75 g/in) and/or less thanabout 23 g/cm (60 g/in).

The sanitary tissue products of the present invention may exhibit aninitial total wet tensile strength of greater than about 118 g/cm (300g/in) and/or greater than about 157 g/cm (400 g/in) and/or greater thanabout 196 g/cm (500 g/in) and/or greater than about 236 g/cm (600 g/in)and/or greater than about 276 g/cm (700 g/in) and/or greater than about315 g/cm (800 g/in) and/or greater than about 354 g/cm (900 g/in) and/orgreater than about 394 g/cm (1000 g/in) and/or from about 118 g/cm (300g/in) to about 1968 g/cm (5000 g/in) and/or from about 157 g/cm (400g/in) to about 1181 g/cm (3000 g/in) and/or from about 196 g/cm (500g/in) to about 984 g/cm (2500 g/in) and/or from about 196 g/cm (500g/in) to about 787 g/cm (2000 g/in) and/or from about 196 g/cm (500g/in) to about 591 g/cm (1500 g/in).

The sanitary tissue products of the present invention may exhibit adensity of less than 0.60 g/cm³ and/or less than 0.30 g/cm³ and/or lessthan 0.20 g/cm³ and/or less than 0.15 g/cm³ and/or less than 0.10 g/cm³and/or less than 0.07 g/cm³ and/or less than 0.05 g/cm³ and/or fromabout 0.01 g/cm³ to about 0.20 g/cm³ and/or from about 0.02 g/cm³ toabout 0.15 g/cm³ and/or from about 0.02 g/cm³ to about 0.10 g/cm³.

The sanitary tissue products of the present invention may be in the formof sanitary tissue product rolls. Such sanitary tissue product rolls maycomprise a plurality of connected, but perforated sheets of fibrousstructure, that are separably dispensable from adjacent sheets.

The sanitary tissue products of the present invention may compriseadditives such as softening agents, temporary wet strength agents,permanent wet strength agents, bulk softening agents, lotions,silicones, wetting agents, latexes, patterned latexes and other types ofadditives suitable for inclusion in and/or on sanitary tissue products.

“Scrim” as used herein means a material that is used to overlay solidadditives within the fibrous structures of the present invention suchthat the solid additives are positioned between the scrim and a layer ofthe fibrous structure. In one example, the scrim covers the solidadditives such that they are positioned between the scrim and thenonwoven substrate of the fibrous structure. In another example, thescrim is a minor component relative to the nonwoven substrate of thefibrous structure.

“Hydroxyl polymer” as used herein includes any hydroxyl-containingpolymer that can be incorporated into a fibrous structure of the presentinvention, such as into a fibrous structure in the form of a fibrouselement. In one example, the hydroxyl polymer of the present inventionincludes greater than 10% and/or greater than 20% and/or greater than25% by weight hydroxyl moieties. In another example, the hydroxyl withinthe hydroxyl-containing polymer is not part of a larger functional groupsuch as a carboxylic acid group.

“Non-thermoplastic” as used herein means, with respect to a material,such as a fibrous element as a whole and/or a polymer within a fibrouselement, that the fibrous element and/or polymer exhibits no meltingpoint and/or softening point, which allows it to flow under pressure, inthe absence of a plasticizer, such as water, glycerin, sorbitol, ureaand the like.

“Thermoplastic” as used herein means, with respect to a material, suchas a fibrous element as a whole and/or a polymer within a fibrouselement, that the fibrous element and/or polymer exhibits a meltingpoint and/or softening point at a certain temperature, which allows itto flow under pressure.

“Non-cellulose-containing” as used herein means that less than 5% and/orless than 3% and/or less than 1% and/or less than 0.1% and/or 0% byweight of cellulose polymer, cellulose derivative polymer and/orcellulose copolymer is present in fibrous element. In one example,“non-cellulose-containing” means that less than 5% and/or less than 3%and/or less than 1% and/or less than 0.1% and/or 0% by weight ofcellulose polymer is present in fibrous element.

“Fast wetting surfactant” as used herein means a surfactant thatexhibits a Critical Micelle Concentration of greater 0.15% by weightand/or at least 0.25% and/or at least 0.50% and/or at least 0.75% and/orat least 1.0% and/or at least 1.25% and/or at least 1.4% and/or lessthan 10.0% and/or less than 7.0% and/or less than 4.0% and/or less than3.0% and/or less than 2.0% by weight.

“Aqueous polymer melt composition” as used herein means a compositioncomprising water and a melt processed polymer, such as a melt processedfibrous element-forming polymer, for example a melt processed hydroxylpolymer.

“Melt processed fibrous element-forming polymer” as used herein meansany polymer, which by influence of elevated temperatures, pressureand/or external plasticizers may be softened to such a degree that itcan be brought into a flowable state, and in this condition may beshaped as desired.

“Melt processed hydroxyl polymer” as used herein means any polymer thatcontains greater than 10% and/or greater than 20% and/or greater than25% by weight hydroxyl groups and that has been melt processed, with orwithout the aid of an external plasticizer. More generally, meltprocessed hydroxyl polymers include polymers, which by the influence ofelevated temperatures, pressure and/or external plasticizers may besoftened to such a degree that they can be brought into a flowablestate, and in this condition may be shaped as desired.

“Blend” as used herein means that two or more materials, such as afibrous element-forming polymer, for example a hydroxyl polymer, and anon-hydroxyl polymer and/or a fast wetting surfactant are in contactwith each other, such as mixed together homogeneously ornon-homogeneously, within a polymeric structure, such as a fibrouselement. In other words, a polymeric structure, such as a fibrouselement, formed from one material, but having an exterior coating ofanother material is not a blend of materials for purposes of the presentinvention. However, a fibrous element formed from two differentmaterials is a blend of materials for purposes of the present inventioneven if the fibrous element further comprises an exterior coating of amaterial.

“Associate,” “Associated,” “Association,” and/or “Associating” as usedherein with respect to fibrous elements means combining, either indirect contact or in indirect contact, fibrous elements such that afibrous structure is formed. In one example, the associated fibrouselements may be bonded together for example by adhesives and/or thermalbonds. In another example, the fibrous elements may be associated withone another by being deposited onto the same fibrous structure makingbelt.

“Weight average molecular weight” as used herein means the weightaverage molecular weight as determined using gel permeationchromatography as generally described in Colloids and Surfaces A.Physico Chemical & Engineering Aspects, Vol. 162, 2000, pg. 107-121 anddetailed in the Weight Average Molecular Weight Test Method describedherein.

“Average Diameter” as used herein, with respect to a fibrous element, ismeasured according to the Average Diameter Test Method described herein.In one example, a fibrous element of the present invention exhibits anaverage diameter of less than 50 nm and/or less than 25 nm and/or lessthan 20 nm and/or less than 15 nm and/or less than 10 nm and/or lessthan 6 nm and/or greater than 1 nm and/or greater than 3 nm as measuredaccording to the Average Diameter Test Method described herein.

“Basis Weight” as used herein is the weight per unit area of a samplereported in lbs/3000 ft² or g/m² as determined by the Basis Weight TestMethod described herein.

“Machine Direction” or “MD” as used herein means the direction parallelto the flow of the fibrous structure through a fibrous structure makingmachine and/or sanitary tissue product manufacturing equipment.Typically, the MD is substantially perpendicular to any perforationspresent in the fibrous structure

“Cross Machine Direction” or “CD” as used herein means the directionperpendicular to the machine direction in the same plane of the fibrousstructure and/or sanitary tissue product comprising the fibrousstructure.

“Ply” or “Plies” as used herein means an individual fibrous structureoptionally to be disposed in a substantially contiguous, face-to-facerelationship with other plies, forming a multiple ply fibrous structure.It is also contemplated that a single fibrous structure can effectivelyform two “plies” or multiple “plies”, for example, by being folded onitself.

As used herein, the articles “a” and “an” when used herein, for example,“an anionic surfactant” or “a fiber” is understood to mean one or moreof the material that is claimed or described.

All percentages and ratios are calculated by weight unless otherwiseindicated. All percentages and ratios are calculated based on the totalcomposition unless otherwise indicated.

Unless otherwise noted, all component or composition levels are inreference to the active level of that component or composition, and areexclusive of impurities, for example, residual solvents or by-products,which may be present in commercially available sources.

Fibrous Elements

The fibrous elements of the present invention comprise a fibrouselement-forming polymer, such as a hydroxyl polymer and a non-hydroxylpolymer. In one example, the fibrous elements may comprise two or morefibrous element-forming polymers, such as two or more hydroxyl polymers.In another example, the fibrous elements may comprise two or morenon-hydroxyl polymer. In another example, the fibrous elements maycomprise two or more non-hydroxyl polymer at least one of which exhibitsa weight average molecular weight of greater than 1,400,000 g/mol and/oris present in the fibrous elements at a concentration greater than itsentanglement concentration (C_(e)) and/or exhibits a polydispersity ofgreater than 1.32. In another example, the fibrous element may comprisetwo or more fibrous element-forming polymers, such as two or morehydroxyl polymers, at least one of which is starch and/or a starchderivative and one of which is a non-starch and/or non-starchderivative, such as polyvinyl alcohol. In one example, the fibrouselement comprises a filament. In another example, the fibrous elementcomprises a fiber.

Fibrous Element-Forming Polymers

The aqueous polymer melt compositions of the present invention and/orfibrous elements, such as filaments and/or fibers, of the presentinvention that associate to form the fibrous structures of the presentinvention contain at least one fibrous element-forming polymer, such asa hydroxyl polymer, and may contain other types of polymers such asnon-hydroxyl polymers that exhibit weight average molecular weights ofgreater than 500,000 g/mol, and mixtures thereof as determined by theWeight Average Molecular Weight Test Method described herein.

Non-limiting examples of hydroxyl polymers in accordance with thepresent invention include polyols, such as polyvinyl alcohol, polyvinylalcohol derivatives, polyvinyl alcohol copolymers, starch, starchderivatives, starch copolymers, chitosan, chitosan derivatives, chitosancopolymers, cellulose, cellulose derivatives such as cellulose ether andester derivatives, cellulose copolymers, hemicellulose, hemicellulosederivatives, hemicellulose copolymers, gums, arabinans, galactans,proteins and various other polysaccharides and mixtures thereof.

In one example, a hydroxyl polymer of the present invention comprises apolysaccharide.

In another example, a hydroxyl polymer of the present inventioncomprises a non-thermoplastic polymer.

The hydroxyl polymer may have a weight average molecular weight of fromabout 10,000 g/mol to about 40,000,000 g/mol and/or greater than 100,000g/mol and/or greater than 1,000,000 g/mol and/or greater than 3,000,000g/mol and/or greater than 3,000,000 g/mol to about 40,000,000 g/mol asdetermined by the Weight Average Molecular Weight Test Method describedherein. Higher and lower molecular weight hydroxyl polymers may be usedin combination with hydroxyl polymers having a certain desired weightaverage molecular weight.

Well known modifications of hydroxyl polymers, such as natural starches,include chemical modifications and/or enzymatic modifications. Forexample, natural starch can be acid-thinned, hydroxy-ethylated,hydroxy-propylated, and/or oxidized. In addition, the hydroxyl polymermay comprise dent corn starch.

Polyvinyl alcohols herein can be grafted with other monomers to modifyits properties. A wide range of monomers has been successfully graftedto polyvinyl alcohol. Non-limiting examples of such monomers includevinyl acetate, styrene, acrylamide, acrylic acid, 2-hydroxyethylmethacrylate, acrylonitrile, 1,3-butadiene, methyl methacrylate,methacrylic acid, vinylidene chloride, vinyl chloride, vinyl amine and avariety of acrylate esters. Polyvinyl alcohols comprise the varioushydrolysis products formed from polyvinyl acetate. In one example thelevel of hydrolysis of the polyvinyl alcohols is greater than 70% and/orgreater than 88% and/or greater than 95% and/or about 99%.

“Polysaccharides” as used herein means natural polysaccharides andpolysaccharide derivatives and/or modified polysaccharides. Suitablepolysaccharides include, but are not limited to, starches, starchderivatives, starch copolymers, chitosan, chitosan derivatives, chitosancopolymers, cellulose, cellulose derivatives, cellulose copolymers,hemicellulose, hemicellulose derivatives, hemicelluloses copolymers,gums, arabinans, galactans, and mixtures thereof. The polysaccharide mayexhibit a weight average molecular weight of from about 10,000 to about40,000,000 g/mol and/or greater than about 100,000 and/or greater thanabout 1,000,000 and/or greater than about 3,000,000 and/or greater thanabout 3,000,000 to about 40,000,000 as determined by the Weight AverageMolecular Weight Test Method described herein.

The polysaccharides of the present invention may comprise non-celluloseand/or non-cellulose derivative and/or non-cellulose copolymer hydroxylpolymers. Non-limiting example of such non-cellulose polysaccharides maybe selected from the group consisting of: starches, starch derivatives,starch copolymers, chitosan, chitosan derivatives, chitosan copolymers,hemicellulose, hemicellulose derivatives, hemicelluloses copolymers, andmixtures thereof.

In one example, the hydroxyl polymer comprises starch, a starchderivative and/or a starch copolymer. In another example, the hydroxylpolymer comprises starch and/or a starch derivative. In yet anotherexample, the hydroxyl polymer comprises starch. In one example, thehydroxyl polymer comprises ethoxylated starch. In another example, thehydroxyl polymer comprises acid-thinned starch.

As is known, a natural starch can be modified chemically orenzymatically, as well known in the art. For example, the natural starchcan be acid-thinned, hydroxy-ethylated, hydroxy-propylated,ethersuccinylated or oxidized. In one example, the starch comprises ahigh amylopectin natural starch (a starch that contains greater than 75%and/or greater than 90% and/or greater than 98% and/or about 99%amylopectin). Such high amylopectin natural starches may be derived fromagricultural sources, which offer the advantages of being abundant insupply, easily replenishable and relatively inexpensive. Chemicalmodifications of starch typically include acid or alkaline-catalyzedhydrolysis and chain scission (oxidative and/or enzymatic) to reducemolecular weight and molecular weight distribution. Suitable compoundsfor chemical modification of starch include organic acids such as citricacid, acetic acid, glycolic acid, and adipic acid; inorganic acids suchas hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, boricacid, and partial salts of polybasic acids, e.g., KH₂PO₄, NaHSO₄; groupIa or IIa metal hydroxides such as sodium hydroxide, and potassiumhydroxide; ammonia; oxidizing agents such as hydrogen peroxide, benzoylperoxide, ammonium persulfate, potassium permanganate, hypochloricsalts, and the like; and mixtures thereof.

“Modified starch” is a starch that has been modified chemically orenzymatically. The modified starch is contrasted with a native starch,which is a starch that has not been modified, chemically or otherwise,in any way.

Chemical modifications may also include derivatization of starch byreaction of its hydroxyl groups with alkylene oxides, and other ether-,ester-, urethane-, carbamate-, or isocyanate-forming substances.Hydroxyalkyl, ethersuccinylated, acetyl, or carbamate starches ormixtures thereof can be used as chemically modified starches. The degreeof substitution of the chemically modified starch is from 0.001 to 3.0,and more specifically from 0.003 to 0.2. Biological modifications ofstarch may include bacterial digestion of the carbohydrate bonds, orenzymatic hydrolysis using enzymes such as amylase, amylopectase, andthe like.

Generally, all kinds of natural starches can be used in the presentinvention. Suitable naturally occurring starches can include, but arenot limited to: corn starch, potato starch, sweet potato starch, wheatstarch, sago palm starch, tapioca starch, rice starch, soybean starch,arrow root starch, amioca starch, bracken starch, lotus starch, waxymaize starch, and high amylose corn starch. Naturally occurringstarches, particularly corn starch and wheat starch, can be particularlybeneficial due to their low cost and availability.

In order to generate the required rheological properties for high-speedspinning processes, the molecular weight of the natural, unmodifiedstarch should be reduced. The optimum molecular weight is dependent onthe type of starch used. For example, a starch with a low level ofamylose component, such as a waxy maize starch, disperses rather easilyin an aqueous solution with the application of heat and does notretrograde or recrystallize significantly. With these properties, a waxymaize starch can be used at a weight average molecular weight, forexample in the range of 500,000 g/mol to 40,000,000 g/mol as determinedby the Weight Average Molecular Weight Test Method described herein.Modified starches such as hydroxy-ethylated Dent corn starch, whichcontains about 25% amylose, or oxidized Dent corn starch tend toretrograde more than waxy maize starch but less than acid thinnedstarch. This retrogradation, or recrystallization, acts as a physicalcross-linking to effectively raise the weight average molecular weightof the starch in aqueous solution. Therefore, an appropriate weightaverage molecular weight for a typical commercially availablehydroxyethylated Dent corn starch with 2 wt. % hydroxyethylation oroxidized Dent corn starch is from about 200,000 g/mol to about10,000,000 g/mol. For ethoxylated starches with higher degrees ofethoxylation, for example a hydroxyethylated Dent corn starch with 5 wt% hydroxyethylation, weight average molecular weights of up to40,000,000 g/mol as determined by the Weight Average Molecular WeightTest Method described herein may be suitable for the present invention.For acid thinned Dent corn starch, which tends to retrograde more thanoxidized Dent corn starch, the appropriate weight average molecularweight is from about 100,000 g/mol to about 15,000,000 g/mol asdetermined by the Weight Average Molecular Weight Test Method describedherein.

The weight average molecular weight of starch may also be reduced to adesirable range for the present invention by physical/mechanicaldegradation (e.g., via the thermomechanical energy input of theprocessing equipment).

The natural starch can be hydrolyzed in the presence of an acid catalystto reduce the molecular weight and molecular weight distribution of thecomposition. The acid catalyst can be selected from the group consistingof hydrochloric acid, sulfuric acid, phosphoric acid, citric acid,ammonium chloride and any combination thereof. Also, a chain scissionagent may be incorporated into a spinnable starch composition such thatthe chain scission reaction takes place substantially concurrently withthe blending of the starch with other components. Non-limiting examplesof oxidative chain scission agents suitable for use herein includeammonium persulfate, hydrogen peroxide, hypochlorite salts, potassiumpermanganate, and mixtures thereof. Typically, the chain scission agentis added in an amount effective to reduce the weight average molecularweight of the starch to the desirable range. It is found thatcompositions having modified starches in the suitable weight averagemolecular weight ranges have suitable shear viscosities, and thusimprove processability of the composition. The improved processabilityis evident in less interruptions of the process (e.g., reduced breakage,shots, defects, hang-ups) and better surface appearance and strengthproperties of the final product, such as fibers of the presentinvention.

In one example, the fibrous element of the present invention is void ofthermoplastic, water-insoluble polymers.

Non-Hydroxyl Polymers

The aqueous polymer melt compositions of the present invention and/orfibrous elements of the present invention comprises, in addition to thefibrous element-forming polymer, one or more non-hydroxyl polymers.

Non-limiting examples of suitable non-hydroxyl polymers that may beincluded in the fibrous elements of the present invention includenon-hydroxyl polymers that exhibit a weight average molecular weight ofgreater than 500,000 g/mol and/or greater than 750,000 g/mol and/orgreater than 1,000,000 g/mol and/or greater than 1,250,000 g/mol and/orat greater than 1,400,000 g/mol and/or at least 1,450,000 g/mol and/orat least 1,500,000 g/mol and/or less than 10,000,000 g/mol and/or lessthan 5,000,000 g/mol and/or less than 2,500.00 g/mol and/or less than2,000,000 g/mol and/or less than 1,750,000 g/mol as determined by theWeight Average Molecular Weight Test Method described herein.

In one example, the non-hydroxyl polymer exhibits a polydispersity ofgreater than 1.10 and/or at least 1.20 and/or at least 1.30 and/or atleast 1.32 and/or at least 1.33 and/or at least 1.35 and/or at least1.40 and/or at least 1.45.

In another example, the non-hydroxyl polymer exhibits a concentrationgreater than its entanglement concentration (Ce) and/or a concentrationgreater than 1.2 times its entanglement concentration (Ce) and/or aconcentration greater than 1.5 times its entanglement concentration (Ce)and/or a concentration greater than twice its entanglement concentration(Ce) and/or a concentration greater than 3 times its entanglementconcentration (Ce).

In yet another example, the non-hydroxyl polymer comprises a linearpolymer. In another example, the non-hydroxyl polymer comprises a longchain branched polymer. In still another example, the non-hydroxylpolymer is compatible with the hydroxyl polymer at a concentrationgreater than the non-hydroxyl polymer's entanglement concentrationC_(e).

Non-limiting examples of suitable non-hydroxyl polymers are selectedfrom the group consisting of: polyacrylamide and its derivatives;polyacrylic acid, polymethacrylic acid and their esters;polyethyleneimine; copolymers made from mixtures of the aforementionedpolymers; and mixtures thereof. In one example, the non-hyrdoxyl polymercomprises polyacrylamide. In one example, the fibrous elements comprisestwo or more non-hydroxyl polymers, such as two or more polyacrylamides,such at two or more different weight average molecular weightpolyacrylamides.

Non-hydroxyl polymers which are substantially compatible with starch arealso useful herein as an extensional viscosity spinning aid.“Substantially compatible” means that the non-hydroxyl polymer does notexist as a separate polymer phase from the fibrous element-formingpolymer, such as the hydroxyl polymer. The molecular weight of asuitable polymer should be sufficiently high to effectuate entanglementsthus increasing the melt strength of the aqueous polymer meltcomposition in which it is present, and preventing melt fracture duringspinning of the aqueous polymer melt composition to produce fibrouselements.

In one example, the non-hydroxyl polymer is at a sufficientconcentration and molecular weight such that the polymer chains of thenon-hydroxyl polymer are overlapped and form entanglement couplings. Forexample, the non-hydroxyl polymer concentration is above theentanglement concentration (c_(e)), where c_(e) is either measured orcalculated. For neutral polymers, such as polyacrylamide, in a goodsolvent, such as water (or other solvent where Rg˜N^(0.6) where Rg isthe polymer's radius of gyration and N is the polymer molecular weight)or polyelectrolytes in the high salt limit, the following scalingrelationships set forth below in Equation (Eq.) (1) apply.η₀ ˜c ^(1.25) c<c _(e)η₀ ˜c ^(4.6) c>c _(e)  (1)Thus, c_(e) is experimentally measured by finding the inflection pointin the dependence of zero shear viscosity (η₀) on concentration. Theentanglement concentration is also calculated from Eq. (2) below,

$\begin{matrix}{c_{e} = \frac{M_{c}}{M_{w}}} & (2)\end{matrix}$where M_(c) is the critical entanglement molecular weight of the polymerspecies, and M_(w) is the weight average molecular weight. For example,a polyacrylamide (PAAm) with an M_(w) of 10,000,000 g/mol must bepresent at ˜0.1% (M_(c) of PAAm is 9100 g/mol) for sufficiententanglement between chains. For c<c_(e), lack of entanglement couplingsresult in inadequate melt strength, while for c>>c_(e) the filament willresist attenuation due to the high degree of strain hardening and meltelasticity. From Eq. (2) a higher or lower molecular weight polymer maybe utilized if its concentration is adjusted accordingly such that thePAAm level is above c_(e).

In one example, the non-hydroxyl polymer comprises a substantiallylinear chain structure, though a non-hydroxyl polymer having a linearchain having short branches (1-5 monomer units) may also be suitable foruse herein. Typically the weight average molecular weight of thenon-hydroxyl polymer ranges from about 500,000 g/mol to 10,000,000 g/moland/or from about 700,000 g/mol to about 5,000,000 g/mol and/or fromabout 1,000,000 g/mol to about 5,000,000 g/mol as determined by theWeight Average Molecular Weight Test Method described herein. In themelt processing of the aqueous polymer melt composition of the presentinvention prior to forming the fibrous elements, the weight averagemolecular weight of the non-hydroxyl polymer may be degraded by shear toabout 1,000,000 g/mol to 3,000,000 g/mol as determined by analysis ofthe fibrous structure with the Degradation of Fibrous Structure TestMethod, described herein followed by the Weight Average Molecular WeightMethod described herein. Typically, the non-hydroxyl polymers arepresent in an amount of from about 0.01% to about 10% and/or from about0.05% to about 5% and/or from about 0.075% to about 2.5% and/or fromabout 0.1% to about 1%, by weight of the aqueous polymer meltcomposition, polymeric structure, fibrous element and/or fibrousstructure.

Since non-hydroxyl polymers are shear sensitive it is important thatM_(w) from Eq. (2) is the chain length after the non-hydroxyl polymerhas been degraded through the melt processing and is in the finalfibrous element composition. The average chain length of thenon-hydroxyl polymer after melt processing is determined by acombination of the Degradation of Fibrous Structure Test Method followedby the Weight Average Molecular Weight Method both methods describedherein.

Non-limiting examples of suitable non-hydroxyl polymers includepolyacrylamide and derivatives such as carboxyl modified polyacrylamidepolymers and copolymers including polyacrylic, poly(hydroxyethylacrylic), polymethacrylic acid and their partial esters; vinyl polymersincluding polyvinylalcohol, polyvinylpyrrolidone, and the like;polyamides; polyalkylene oxides such as polyethylene oxide and mixturesthereof. Copolymers or graft copolymers made from mixtures of monomersselected from the aforementioned polymers are also suitable herein.Non-limiting examples of commercially available polyacrylamides includenonionic polyacrylamides such as N300 from Kemira or Hyperfloc® NF221,NF301, and NF241 from Hychem, Inc.

Surfactants

The aqueous polymer melt compositions of the present invention and/orfibrous elements of the present invention and fibrous structures formedthereform may comprise one or more surfactants. In one example, thesurfactant is a fast wetting surfactant. In another example, thesurfactant comprises a non-fast wetting surfactant, such as Aerosol® OTfrom Cytec.

Non-limiting examples of suitable fast wetting surfactants includesurfactants that exhibit a twin-tailed general structure, for example asurfactant that exhibits a structure IA or IB as follows.

wherein R is independently selected from substituted or unsubstituted,linear or branched aliphatic groups and mixtures thereof. In oneexample, R is independently selected from substituted or unsubstituted,linear or branched C₄-C₇ aliphatic chains and mixtures thereof. Inanother example, R is independently selected from substituted orunsubstituted, linear or branched C₄-C₇ alkyls and mixtures thereof. Inanother example, R is independently selected from substituted orunsubstituted, linear or branched C₅-C₆ alkyls and mixtures thereof. Instill another example, R is independently selected from substituted orunsubstituted, linear or branched C₆ alkyls and mixtures thereof. Ineven another example, R is an unsubstituted, branched C₆ alkyl havingthe following structure II.

In another example, R is independently selected from substituted orunsubstituted, linear or branched C₅ alkyls and mixtures thereof. In yetanother example, R is independently selected from unsubstituted, linearC₅ alkyls and mixtures thereof. The C₅ alkyl may comprise a mixture ofunsubstituted linear C₅ alkyls, for example C₅ n-pentyl, and/or 1-methylbranched C₅ alkyls as shown in the following structure III.

In even another example, R comprises a mixture of C₄-C₇ alkyls and/or amixture of C₅-C₆ alkyls.

The fast wetting surfactants may be present in the polymer meltcompositions, fibrous elements, and/or fibrous structures of the presentinvention, alone or in combination with other non-fast wettingsurfactants.

In one example, the fast wetting surfactants of the present inventionmay be used individually or in mixtures with each other or in a mixturewith one or more non-fast wetting surfactants, for example a C₈sulfosuccinate surfactant where R is the following structure IV

In one example a fast wetting surfactant comprises a sulfosuccinatesurfactant having the following structure V.

wherein R is independently selected from substituted or unsubstituted,linear or branched aliphatic groups and mixtures thereof. In oneexample, R is independently selected from substituted or unsubstituted,linear or branched C₄-C₇ aliphatic chains and mixtures thereof. Inanother example, R is independently selected from substituted orunsubstituted, linear or branched C₄-C₇ alkyls and mixtures thereof. Inanother example, R is independently selected from substituted orunsubstituted, linear or branched C₅-C₆ alkyls and mixtures thereof. Instill another example, R is independently selected from substituted orunsubstituted, linear or branched C₆ alkyls and mixtures thereof. Ineven another example, R is an unsubstituted, branched C₆ alkyl havingthe following structure II.

Non-limiting examples of fast wetting surfactants according to thepresent invention include sulfosuccinate surfactants, for example asulfosuccinate surfactant that has structure II as its R groups(Aerosol® MA-80), a sulfosuccinate surfactant that has C₄ isobutyl asits R groups (Aerosol® IB), and a sulfosuccinate surfactant that has amixture of C₅ n-pentyl and structure III as its R groups (Aerosol® AY),all commercially available from Cytec.

Additional non-limiting examples of fast wetting surfactants accordingto the present invention include alcohol sulfates derived from branchedalcohols such as Isalchem and Lial alcohols (from Sasol) ie. Dacpon 2723 AS and Guerbet alcohols from Lucky Chemical. Still another example ofa fast wetting surfactant includes paraffin sulfonates such as HostapurSAS30 from Clariant.

Typically, the fast wetting surfactants are present in an amount of fromabout 0.01% to about 5% and/or from about 0.5% to about 2.5% and/or fromabout 1% to about 2% and/or from about 1% to about 1.5%, by weight ofthe aqueous polymer melt composition, polymeric structure, fibrouselement and/or fibrous structure.

In one example, the fast wetting surfactants of the present inventionexhibit a Minimum Surface Tension in Distilled Water of less than 34.0and/or less than 33.0 and/or less than 32.0 and/or less than 31.0 and/orless than 30.0 and/or less than 29.0 and/or less than 28.0 and/or lessthan 27.0 and/or less than 26.75 and/or less than 26.5 and/or less than26.2 and/or less than 25.0 mN/m and/or to greater than 0 and/or greaterthan 1.0 mN/m.

In still another example, the fast wetting surfactants of the presentinvention exhibit a CMC of greater than 0.15% and/or at least 0.25%and/or at least 0.50% and/or at least 0.75% and/or at least 1.0% and/orat least 1.25% and/or at least 1.4% and/or less than 10.0% and/or lessthan 7.0% and/or less than 4.0% and/or less than 3.0% and/or less than2.0% by weight and a Minimum Surface Tension in Distilled Water of lessthan 34.0 and/or less than 33.0 and/or less than 32.0 and/or less than31.0 and/or less than 30.0 and/or less than 29.0 and/or less than 28.0and/or less than 27.0 and/or less than 26.75 and/or less than 26.5and/or less than 26.2 and/or less than 25.0 mN/m and/or to greater than0 and/or greater than 1.0 mN/m. In even another example, the fastwetting surfactants of the present invention exhibit a CMC of at least1.0% and/or at least 1.25% and/or at least 1.4% and/or less than 4.0%and/or less than 3.0% and/or less than 2.0% by weight and a MinimumSurface Tension in Distilled Water of less than 34.0 and/or less than33.0 and/or less than 32.0 and/or less than 31.0 and/or less than 30.0and/or less than 29.0 and/or less than 28.0 and/or less than 27.0 and/orless than 26.75 and/or less than 26.5 and/or less than 26.2 and/or lessthan 25.0 mN/m and/or to greater than 0 and/or greater than 1.0 mN/m.CMC and Minimum Surface Tension in Distilled Water values of surfactantscan be measured by any suitable methods known in the art, for examplethose methods described in Principles of Colloid and Surface Chemistry,p 370-375, incorporated herein by reference.

Table 1 below shows properties of a non-fast wetting surfactant, threefast wetting surfactants, and one mixture of a fast wetting surfactantand a non-fast wetting surfactant, alone and in fibrous elements thatform a fibrous structure and compared to a fibrous structure comprisingfibrous elements that are void of surfactants. As mentioned above, theCMC and Minimum Surface Tension in Distilled Water are measured by anysuitable method known in the art, for example the methods described inPaul C. Hiemenz and Raj Rajagopalan, Principles of Colloid and SurfaceChemistry 3^(rd) Edition, p 253-255, incorporated herein by reference.The wetting rate of a fibrous structure is determined by the WettingRate Test Method described herein with from 0.5% to 1.5% by weight totalsurfactant in the fibrous structure.

TABLE 1 Minimum Surface Tension in R Aliphatic CMC Distilled WaterWetting Surfactant Group wt % (mN/m) Rate No Surfactant NA NA NA −78Aerosol ® OT C₈ (IV) 0.10-0.15 26.2 −185 (AOT) Non-Fast WettingSurfactant Fast Wetting C₆ (II) 1.4 27.0 −248 Surfactant 1 (Aerosol ®MA- 80) (AMA) Fast Wetting C₅ (III) 1.8 30.1 −339 Surfactant 2(Aerosol ® AY) (AAY) Fast Wetting C₄ 4.0 30.1 −323 Surfactant 3(Aerosol ® IB) (AIB) Fast Wetting NA NA NA −295 Surfactant Mixture (2:1Aerosol ® OT/Aerosol ® MA-80)

In one example, fibrous structures comprising fibrous elements of thepresent invention that comprise one or more fast wetting surfactantssuch that the total level of fast wetting surfactant present in thefibrous structure is from 0.5% to about 1.5% by weight exhibit a wettingrate of less than −185 and/or less than −190 and/or less than −200and/or less than −245 and/or less than −275 and/or less than −300 and/orless than −320 as measured by the Wetting Rate Test Method describedherein.

Fast wetting surfactants according to the present may also becharacterized by having structures that are not substantially complexedby the amylose portion of starch. If the amylose complexes thesurfactant in the aqueous polymer melt composition, there is lesssurfactant at the water-air interface of the incipient fibrous elementsbeing formed to lower the surface tension. In addition, the presence ofamylose-surfactant complex decreases the dry fibrous structure tensileproperties as measured by the Dry Tensile Test Method described herein.The presence of an amylose-surfactant complex can be determined from theDetermination of Total Free Surfactant in Fibrous Structure Using WaterExtraction/HPLC Test Method described herein. For example, a fibrousstructure produced from fibrous elements prepared with 1.3% of anon-fast wetting surfactant; namely, Aerosol® OT (IV) was analyzed bythe Determination of Total Free Surfactant in Fibrous Structure UsingWater Extraction/HPLC Test Method described herein. The extractcontained only 0.49% Aerosol® OT (38% recovery), the rest of theAerosol® OT surfactant remained with the fibrous structure. In contrast,extract from a fibrous structure produced from fibrous elements preparedwith 1.3% of a fast wetting surfactant namely; Aerosol® MA-80 (II),contained 1.1% Aerosol® MA-80 (85% recovery) with only 0.2% Aerosol®MA-80 remaining with the fibrous structure. The fibrous elements of thepresent invention, which contain one or more fast wetting surfactants ofthe present invention, produce fibrous structures having greater than50% fast wetting surfactant recovery after extraction with wateraccording to the Determination of Total Free Surfactant in FibrousStructure Using Water Extraction/HPLC Test Method described herein. Inone example, the fast wetting surfactants of the present invention thatdo not complex to amylose have chainlengths of less than 8 carbons andthe chains have some degree of branching.

In one example, the fast wetting surfactants of the present exhibitsurface tensions of less than 39 mN/m² after 0.1 seconds at a fastwetting surfactant concentration of 1 g/liter at 25° C. as measured withthe Dynamic Surface Tension (“Bubble Pressure”) Test Method described inStanislav Dukhin, Gunter Kretzschmar, Reinhard Miller, Dynamics ofAdsorption at Liquid Interfaces: Theory, Experiment, Application, p 157,incorporated herein by reference. This test method uses a 0.1-2.5%solution of amylose instead of distilled water to probe whether the fastwetting surfactant is complexed by amylose.

A fast wetting surfactant may be present both in the interior andexterior of the fibrous elements produced from the aqueous polymer meltcomposition, which is distinguished from a surface only treatment of theformed fibrous elements. Any fast wetting surfactant that is present onthe exterior of a fibrous element may be determined by extracting thefibrous element with a solvent that dissolves the surfactant, but doesnot swell the fibrous element and then analyzing for the surfactant byLC-mass spec. The surfactant that is present in the interior of thefibrous element may be determined by extracting the fibrous element witha solvent that dissolves the surfactant and also swells the fibrouselements, such as water/alcohol or water/acetone mixtures followed byanalysis for surfactant by a technique such as LC mass spec.Alternatively, the fibrous element may be treated with an enzyme such asamylase that degrades the fibrous element-forming polymer, for examplepolysaccharide, but not the fast wetting surfactant and the resultingsolution may be analyzed for the surfactant by LC-mass spec.

Solid Additives

The fibrous structures and/or sanitary tissue products of the presentinvention may further comprise one or more solid additives. “Solidadditive” as used herein means an additive that is capable of beingapplied to a surface of a fibrous structure in a solid form. In otherwords, the solid additive of the present invention can be delivereddirectly to a surface of a nonwoven substrate without a liquid phasebeing present, i.e. without melting the solid additive and withoutsuspending the solid additive in a liquid vehicle or carrier. As such,the solid additive of the present invention does not require a liquidstate or a liquid vehicle or carrier in order to be delivered to asurface of a nonwoven substrate. The solid additive of the presentinvention may be delivered via a gas or combinations of gases. In oneexample, in simplistic terms, a solid additive is an additive that whenplaced within a container, does not take the shape of the container.

The solid additives of the present invention may have differentgeometries and/or cross-sectional areas that include round, elliptical,star-shaped, rectangular, trilobal and other various eccentricities.

In one example, the solid additive may exhibit a particle size of lessthan 6 mm and/or less than 5.5 mm and/or less than 5 mm and/or less than4.5 mm and/or less than 4 mm and/or less than 2 mm in its maximumdimension.

“Particle” as used herein means an object having an aspect ratio of lessthan about 25/1 and/or less than about 15/1 and/or less than about 10/1and/or less than 5/1 to about 1/1. A particle is not a fiber as definedherein.

The solid additives may be present in the fibrous structures of thepresent invention at a level of greater than about 1 and/or greater thanabout 2 and/or greater than about 4 and/or to about 20 and/or to about15 and/or to about 10 g/m². In one example, a fibrous structure of thepresent invention comprises from about 2 to about 10 and/or from about 5to about 10 g/m² of solid additive.

In one example, the solid additives are present in the fibrousstructures of the present invention at a level of greater than 5% and/orgreater than 10% and/or greater than 20% to about 50% and/or to about40% and/or to about 30%.

Non-limiting examples of solid additives of the present inventioninclude fibers, for example pulp fibers. Non-limiting examples of pulpfibers include hardwood pulp fibers, softwood pulp fibers, and mixturesthereof. In one example, the solid additives comprise eucalyptus pulpfibers. In another example, the solid additives include chemicallytreated pulp fibers.

Scrim Material

The fibrous structure and/or sanitary tissue product may furthercomprise a scrim material. The scrim material may comprise any suitablematerial capable of bonding to the nonwoven substrate of the presentinvention. In one example, the scrim material comprises a material thatcan be thermally bonded to the nonwoven substrate of the presentinvention. Non-limiting examples of suitable scrim materials includefilaments of the present invention. In one example, the scrim materialcomprises filaments that comprise hydroxyl polymers. In another example,the scrim material comprises starch filaments. In yet another example,the scrim material comprises filaments comprising a thermoplasticpolymer. In still another example, the scrim material comprises afibrous structure according to the present invention wherein the fibrousstructure comprises filaments comprising hydroxyl polymers, such asstarch filaments, and/or thermoplastic polymers. In another example, thescrim material may comprise a film. In another example, the scrimmaterial may comprise a nonwoven substrate according to the presentinvention. In even another example, the scrim material may comprise alatex.

In one example, solid additives are positioned between the scrimmaterial and the nonwoven substrate, for example a surface of thenonwoven substrate. The scrim material may be connected to a surface ofthe nonwoven substrate, for example at one or more bond sites.

In one example, the scrim material may be the same composition as thenonwoven substrate.

The scrim material may be present in the fibrous structures of thepresent invention at a basis weight of greater than 0.1 and/or greaterthan 0.3 and/or greater than 0.5 and/or greater than 1 and/or greaterthan 2 g/m² and/or less than 10 and/or less than 7 and/or less than 5and/or less than 4 g/m² as determined by the Basis Weight Test Methoddescribed herein.

Methods of the Present Invention

The methods of the present invention relate to producing polymericstructures, such as fibrous elements, from aqueous polymer meltcompositions comprising a fibrous element-forming polymer, such as ahydroxyl polymer, and a fast wetting surfactant.

Methods for Making Fibrous Structure

FIGS. 1 and 2 illustrate one example of a method for making a fibrousstructure of the present invention. As shown in FIGS. 1 and 2 , themethod 10 comprises the steps of:

a. providing first filaments 12 from a first source 14 of filaments,which form a first layer 16 of filaments;

b. providing second filaments 18 from a second source 20 of filaments,which form a second layer 22 of filaments;

c. providing third filaments 24 from a third source 26 of filaments,which form a third layer 28 of filaments;

d. providing solid additives 30 from a source 32 of solid additives;

e. providing fourth filaments 34 from a fourth source 36 of filaments,which form a fourth layer 38 of filaments; and

f. collecting the first, second, third, and fourth filaments 12, 18, 24,34 and the solid additives 30 to form a fibrous structure 40, whereinthe first source 14 of filaments is oriented at a first angle α to themachine direction of the fibrous structure 40, the second source 20 offilaments is oriented at a second angle β to the machine directiondifferent from the first angle α, the third source 26 is oriented at athird angle δ to the machine direction different from the first angle αand the second angle β, and wherein the fourth source 36 is oriented ata fourth angle ϵ to the machine direction different from the secondangle β and third angle δ.

The first, second, and third layers 16, 22, 28 of filaments arecollected on a collection device 42, which may be a belt or fabric. Thecollection device 42 may be a patterned belt that imparts a pattern,such as a non-random, repeating pattern to the fibrous structure 40during the fibrous structure making process. The first, second, andthird layers 16, 22, 28 of filaments are collected (for example one ontop of the other) on the collection device 42 to form a multi-layernonwoven substrate 44 upon which the solid additives 30 are deposited.The fourth layer 38 of filaments may then be deposited onto the solidadditives 30 to form a scrim 46.

The first angle α and the fourth angle ϵ may be the same angle, forexample 90° to the machine direction.

The second angle β and the third angle δ may be the same angle, justpositive and negative of one another. For example the second angle β maybe −40° to the machine direction and the third angle δ may be +40° tothe machine direction.

In one example, at least one of the first, second, and third angles α,β, δ is less than 90° to the machine direction. In another example, thefirst angle α and/or fourth angle c is about 90° to the machinedirection. In still another example, the second angle β and/or thirdangle δ is from about ±10° to about ±80° and/or from about ±30° to about±60° to the machine direction and/or about ±40° to the machinedirection.

In one example, the first, second, and third layers 16, 22, 28 offilaments may be formed into a nonwoven substrate 44 prior to beingutilized in the process for making a fibrous structure described above.In this case, the nonwoven substrate 44 would likely be in a parent rollthat could be unwound into the fibrous structure making process and thesolid additives 30 could be deposited directly onto a surface of thenonwoven substrate 44.

In one example, the step of providing a plurality of solid additives 30onto the nonwoven substrate 44 may comprise airlaying the solidadditives 30 using an airlaying former. A non-limiting example of asuitable airlaying former is available from Dan-Web of Aarhus, Denmark.

In one example, the step of providing fourth filaments 34 such that thefilaments contact the solid additives 30 comprises the step ofdepositing the fourth filaments 34 such that at least a portion (in oneexample all or substantially all) of the solid additives 30 arecontacted by the fourth filaments 34 thus positioning the solidadditives 30 between the fourth layer 38 of filaments and the nonwovensubstrate 44. Once the fourth layer 38 of filaments is in place, thefibrous structure 40 may be subjected to a bonding step that bonds thefourth layer 38 of filaments (in this case, the scrim 46) to thenonwoven substrate 44. This step of bonding may comprise a thermalbonding operation. The thermal bonding operation may comprise passingthe fibrous structure 40 through a nip formed by thermal bonding rolls48, 50. At least one of the thermal bonding rolls 48, 50 may comprise apattern that is translated into the bond sites 52 formed in the fibrousstructure 40.

In addition to being subjected to a bonding operation, the fibrousstructure may also be subjected to other post-processing operations suchas embossing, tuft-generating, gear rolling, which includes passing thefibrous structure through a nip formed between two engaged gear rolls,moisture-imparting operations, free-fiber end generating, and surfacetreating to form a finished fibrous structure. In one example, thefibrous structure is subjected to gear rolling by passing the fibrousstructure through a nip formed by at least a pair of gear rolls. In oneexample, the fibrous structure is subjected to gear rolling such thatfree-fiber ends are created in the fibrous structure. The gear rollingmay occur before or after two or more fibrous structures are combined toform a multi-ply sanitary tissue product. If it occurs after, then themulti-ply sanitary tissue product is passed through the nip formed by atleast a pair of gear rolls.

The method for making a fibrous structure of the present invention maybe close coupled (where the fibrous structure is convolutedly wound intoa roll prior to proceeding to a converting operation) or directlycoupled (where the fibrous structure is not convolutedly wound into aroll prior to proceeding to a converting operation) with a convertingoperation to emboss, print, deform, surface treat, or other post-formingoperation known to those in the art. For purposes of the presentinvention, direct coupling means that the fibrous structure can proceeddirectly into a converting operation rather than, for example, beingconvolutedly wound into a roll and then unwound to proceed through aconverting operation.

In one example, one or more plies of the fibrous structure according tothe present invention may be combined with another ply of fibrousstructure, which may also be a fibrous structure according to thepresent invention, to form a multi-ply sanitary tissue product thatexhibits a Tensile Ratio of 2 or less and/or less than 1.7 and/or lessthan 1.5 and/or less than 1.3 and/or less than 1.1 and/or greater than0.7 and/or greater than 0.9 as measured according to the Dry TensileTest Method described herein. In one example, the multi-ply sanitarytissue product may be formed by combining two or more plies of fibrousstructure according to the present invention. In another example, two ormore plies of fibrous structure according to the present invention maybe combined to form a multi-ply sanitary tissue product such that thesolid additives present in the fibrous structure plies are adjacent toeach of the outer surfaces of the multi-ply sanitary tissue product.

The process of the present invention may include preparing individualrolls of fibrous structure and/or sanitary tissue product comprisingsuch fibrous structure(s) that are suitable for consumer use.

In one example, the sources of filaments comprise meltblow dies thatproduce filaments from a polymer melt composition according to thepresent invention. In one example, as shown in FIG. 3 the meltblow die54 may comprise at least one filament-forming hole 56, and/or 2 or moreand/or 3 or more rows of filament-forming holes 56 from which filamentsare spun. At least one row of the filament-forming holes 56 contains 2or more and/or 3 or more and/or 10 or more filament-forming holes 56. Inaddition to the filament-forming holes 56, the meltblow die 54 comprisesfluid-releasing holes 58, such as gas-releasing holes, in one exampleair-releasing holes, that provide attenuation to the filaments formedfrom the filament-forming holes 56. One or more fluid-releasing holes 58may be associated with a filament-forming hole 56 such that the fluidexiting the fluid-releasing hole 58 is parallel or substantiallyparallel (rather than angled like a knife-edge die) to an exteriorsurface of a filament exiting the filament-forming hole 56. In oneexample, the fluid exiting the fluid-releasing hole 58 contacts theexterior surface of a filament formed from a filament-forming hole 56 atan angle of less than 30° and/or less than 20° and/or less than 10°and/or less than 5° and/or about 0°. One or more fluid releasing holes58 may be arranged around a filament-forming hole 56. In one example,one or more fluid-releasing holes 58 are associated with a singlefilament-forming hole 56 such that the fluid exiting the one or morefluid releasing holes 58 contacts the exterior surface of a singlefilament formed from the single filament-forming hole 56. In oneexample, the fluid-releasing hole 58 permits a fluid, such as a gas, forexample air, to contact the exterior surface of a filament formed from afilament-forming hole 56 rather than contacting an inner surface of afilament, such as what happens when a hollow filament is formed.

Aqueous Polymer Melt Composition

The aqueous polymer melt composition of the present invention comprisesa melt processed fibrous element-forming polymer, such as a meltprocessed hydroxyl polymer, and a fast wetting surfactant according tothe present invention.

The aqueous polymer melt compositions may already be formed or a meltprocessing step may need to be performed to convert a raw materialfibrous element-forming polymer, such as a hydroxyl polymer, into a meltprocessed fibrous element-forming polymer, such as a melt processedhydroxyl polymer, thus producing the aqueous polymer melt composition.Any suitable melt processing step known in the art may be used toconvert the raw material fibrous element-forming polymer into the meltprocessed fibrous element-forming polymer. “Melt processing” as usedherein means any operation and/or process by which a polymer is softenedto such a degree that it can be brought into a flowable state.

The aqueous polymer melt compositions of the present invention may havea shear viscosity, as measured according to the Shear Viscosity of aPolymer Melt Composition Measurement Test Method described herein, offrom about 0.5 Paseal·Seconds to about 25 Pascal·Seconds and/or fromabout 2 Pascal·Seconds to about 20 Pascal·Seconds and/or from about 3Paseal·Seconds to about 10 Paseal·Seconds, as measured at a shear rateof 3,000 sec⁻¹ and at the processing temperature (50° C. to 100° C.).The aqueous polymer melt compositions may have a thinning index n valueas measured according to the Shear Viscosity of a Polymer MeltComposition Measurement Test Method described herein of from about 0.4to about 1.0 and/or from about 0.5 to about 0.8.

The aqueous polymer melt compositions may have a temperature of fromabout 50° C. to about 100° C. and/or from about 65° C. to about 95° C.and/or from about 70° C. to about 90° C. when spinning fibrous elementsfrom the aqueous polymer melt compositions.

In one example, the polymer melt composition of the present inventionmay comprise from about 30% and/or from about 40% and/or from about 45%and/or from about 50% to about 75% and/or to about 80% and/or to about85% and/or to about 90% and/or to about 95% and/or to about 99.5% byweight of the aqueous polymer melt composition of a fibrouselement-forming polymer, such as a hydroxyl polymer. The fibrouselement-forming polymer, such as a hydroxyl polymer, may have a weightaverage molecular weight greater than 100,000 g/mol as determined by theWeight Average Molecular Weight Test Method described herein prior toany crosslinking.

A fast wetting surfactant is present in the aqueous polymer meltcompositions and/or may be added to the aqueous polymer melt compositionbefore polymer processing of the aqueous polymer melt composition.

A non-hydroxyl polymer, such as polyacrylamide, may be present in theaqueous polymer melt composition and/or may be added to the aqueouspolymer melt composition before polymer processing of the aqueouspolymer melt composition.

A crosslinking system comprising a crosslinking agent, such as animidazolidinone, and optionally, a crosslinking facilitator, such as anammonium salt, may be present in the aqueous polymer melt compositionand/or may be added to the aqueous polymer melt composition beforepolymer processing of the aqueous polymer melt composition.

“Crosslinking agent” as used herein means any material that is capableof crosslinking a hydroxyl polymer within a polymer melt compositionaccording to the present. Non-limiting examples of suitable crosslinkingagents include polycarboxylic acids and/or imidazolidinones.

“Crosslinking facilitator” as used herein means any material that iscapable of activating a crosslinking agent thereby transforming thecrosslinking agent from its unactivated state to its activated state. Inother words, when a crosslinking agent is in its unactivated state, thehydroxyl polymer present in the polymer melt composition does notundergo unacceptable crosslinking. Unacceptable crosslinking causes theshear viscosity and n value to fall outside the ranges specified whichare determined according to the Shear Viscosity of a Polymer MeltComposition Measurement Test Method. In the case of imidazolidinonecrosslinkers (such as dihydroxyethyleneurea “DHEU”), the pH and thetemperature of the Polymer Melt Composition should be in the desiredranges as measured by the pH of Melt Composition Method and Temperatureof Melt Composition Method as described herein; unacceptablecrosslinking occur outside these ranges.

When a crosslinking agent in accordance with the present invention is inits activated state, the hydroxyl polymer present in the polymericstructure may and/or does undergo acceptable crosslinking via thecrosslinking agent as determined according to the Initial Total WetTensile Test Method described herein.

Upon crosslinking the hydroxyl polymer during the curing step, thecrosslinking agent becomes an integral part of the polymeric structureas a result of crosslinking the hydroxyl polymer as shown in thefollowing schematic representation:

Hydroxyl polymer-Crosslinking agent-Hydroxyl polymer

The crosslinking facilitator may include derivatives of the materialthat may exist after the transformation/activation of the crosslinkingagent. For example, a crosslinking facilitator salt being chemicallychanged to its acid form and vice versa.

Nonlimiting examples of suitable crosslinking facilitators include acidshaving a pKa of less than 6 or salts thereof. The crosslinkingfacilitators may be Bronsted Acids and/or salts thereof, such asammonium salts thereof.

In addition, metal salts, such as magnesium and zinc salts, can be usedalone or in combination with Bronsted Acids and/or salts thereof, ascrosslinking facilitators.

Nonlimiting examples of suitable crosslinking facilitators includebenzoic acid, citric acid, formic acid, glycolic acid, lactic acid,maleic acid, phthalic acid, phosphoric acid, hypophosphoric acid,succinic acid, and mixtures thereof and/or their salts, such as theirammonium salts, such as ammonium glycolate, ammonium citrate, ammoniumchloride, ammonium sulfate

Additional non-limiting examples of suitable crosslinking facilitatorsinclude glyoxal bisulfite salts, primary amine salts, such ashydroxyethyl ammonium salts, hydroxypropyl ammonium salt, secondaryamine salts, ammonium toluene sulfonate, ammonium benzene sulfonate,ammonium xylene sulfonate, magnesium chloride, and zinc chloride.

Non-Limiting Example—Synthesis of an Aqueous Polymer Melt Composition

An aqueous polymer melt composition of the present invention may beprepared using screw extruders, such as a vented twin screw extruder.

A barrel 60 of an APV Baker (Peterborough, England) 40:1, 58 mm diametertwin screw extruder is schematically illustrated in FIG. 4A. The barrel60 is separated into eight zones, identified as zones 1-8. The barrel 60encloses the extrusion screw and mixing elements, schematically shown inFIG. 4B, and serves as a containment vessel during the extrusionprocess. A solid feed port 62 is disposed in zone 1, a first liquid feedport 64 is disposed in zone 2, a second liquid feed port 66 is disposedin zone 3, a third liquid feed port 68 is disposed in zone 4, and afourth liquid feed port 70 is disposed in zone 5. A vent 72 is includedin zone 7 for cooling and decreasing the liquid, such as water, contentof the mixture prior to exiting the extruder. An optional vent stuffer,commercially available from APV Baker, can be employed to prevent thepolymer melt composition from exiting through the vent 72. The flow ofthe aqueous polymer melt composition through the barrel 60 is from zone1 exiting the barrel 60 at zone 8.

A screw and mixing element configuration for the twin screw extruder isschematically illustrated in FIG. 4B. The twin screw extruder comprisesa plurality of twin lead screws (TLS) (designated A and B) and paddles(designated C) and reverse twin lead screws (RTLS) (designated D)installed in series as illustrated in Table 1 below.

TABLE 1 Total Length Length Element Zone Ratio Element Pitch Ratio Type1 1.5 TLS 1 1.5 A 1 3.0 TLS 1 1.5 A 1 4.5 TLS 1 1.5 A 2 6.0 TLS 1 1.5 A2 7.5 TLS 1 1.5 A 2 9.0 TLS 1 1.5 A 3 10.5 TLS 1 1.5 A 3 12.0 TLS 1 1.5A 3 13.0 TLS 1 1 A 3 14.0 TLS 1 1 A 4 15.0 TLS 1 1 A 4 16.0 TLS 1 1 A 416.3 PADDLE 0 0.25 C 4 16.5 PADDLE 0 0.25 C 4 18.0 TLS 1 1.5 A 4 19.5TLS 1 1.5 A 5 21.0 TLS 1 1.5 A 5 22.5 TLS 1 1.5 A 5 24.0 TLS 1 1.5 A 525.0 TLS 1 1 A 6 25.3 TLS 1 0.25 A 6 26.3 TLS 1 1 A 6 27.3 TLS 1 1 A 628.3 TLS 0.5 1 B 6 29.3 TLS 0.5 1 B 6 29.8 RTLS 0.5 0.5 D 7 30.3 RTLS0.5 0.5 D 7 30.8 RTLS 0.5 0.5 D 7 32.3 TLS 1 1.5 A 7 33.8 TLS 1 1.5 A 734.8 TLS 1 1 A 8 35.8 TLS 1 1 A 8 36.8 TLS 0.5 1 B 8 37.8 TLS 0.5 1 B 838.8 TLS 0.5 1 B 8 40.3 TLS 0.5 1.5 B

Screw elements (A-B) are characterized by the number of continuous leadsand the pitch of these leads. A lead is a flight (at a given helixangle) that wraps the core of the screw element. The number of leadsindicates the number of flights wrapping the core at any given locationalong the length of the screw. Increasing the number of leads reducesthe volumetric capacity of the screw and increases the pressuregenerating capability of the screw.

The pitch of the screw is the distance needed for a flight to completeone revolution of the core. It is expressed as the number of screwelement diameters per one complete revolution of a flight. Decreasingthe pitch of the screw increases the pressure generated by the screw anddecreases the volumetric capacity of the screw.

The length of a screw element is reported as the ratio of length of theelement divided by the diameter of the element.

This example uses TLS and RTLS. Screw element type A is a TLS with a 1.0pitch and varying length ratios. Screw element type B is a TLS with a0.5 pitch and varying length ratios.

Bilobal paddles, C, serving as mixing elements, are also included inseries with the SLS and TLS screw elements in order to enhance mixing.Paddle C has a length ratio of ¼. Various configurations of bilobalpaddles and reversing elements D, single and twin lead screws threadedin the opposite direction, are used in order to control flow andcorresponding mixing time. Screw element D is a RTLS with a 0.5 pitchand a 0.5 length ratio.

In zone 1, one or more fibrous element-forming polymers, such as one ormore hydroxyl polymers, are fed into the solid feed port 62 at a rate of330 grams/minute using a K-Tron (Pitman, N.J.) loss-in-weight feeder.These hydroxyl polymers are combined inside the extruder (zone 2) with afast wetting surfactant (Aerosol® MA-80) added at liquid feed port 64(zone 2) at a rate of 12 grams/minute. Water, an external plasticizer,is added at the liquid feed port 66 (zone 3) at a rate of 160grams/minute using a Milton Roy (Ivyland, Pa.) diaphragm pump (1.9gallon per hour pump head) to form a hydroxyl polymer/fast wettingsurfactant/water slurry. A crosslinking facilitator, such as ammoniumchloride, may be added to the slurry at liquid feed port 66 (zone 3)also. Another fibrous element-forming polymer, such as a hydroxylpolymer, for example polyvinyl alcohol, may be added to the slurry atliquid feed port 68 (zone 4). A non-hydroxyl polymer, such aspolyacrylamide may be added to the slurry at liquid feed port 70 (zone5). Additional additives such as other surfactants, other non-hydroxylpolymers, other salts and/or acids may be added at various feed portsalong the length of the barrel 60. This slurry is then conveyed down thebarrel 60 of the extruder and cooked to produce an aqueous polymer meltcomposition comprising a melt processed hydroxyl polymer and a fastwetting surfactant. Table 2 describes the temperature, pressure, andcorresponding function of each zone of the extruder.

TABLE 2 Temp. Description Zone (° F.) Pressure of Screw Purpose 1 70 LowFeeding/Conveying Feeding and Mixing 2 70 Low Conveying Mixing andConveying 3 70 Low Conveying Mixing and Conveying 4 130 LowPressure/Decreased Conveying and Heating Conveying 5 355 Medium PressureGenerating Cooking at Pressure and Temperature 6 355 High ReversingCooking at Pressure and Temperature 7 355 Low Conveying Cooling andConveying (with venting) 8 355 Low Pressure Generating Conveying

After the aqueous polymer melt composition exits the first extruder,part of the aqueous polymer melt composition is dumped and another part(450 g) is fed into a Mahr (Charlotte, N.C.) gear pump and pumped to asecond extruder. The second extruder provides a means to cool thepolymer melt composition by venting the polymer melt composition toatmospheric pressure and provides additional points to incorporateadditives. A barrel 74 of an APV Baker (Peterborough, England) 13:1, 70mm diameter twin screw extruder is schematically illustrated in FIG. 5Aas the second extruder. The barrel 74 is separated into five zones,identified as zones 1-5. The barrel 74 encloses the extrusion screw andmixing elements, schematically shown in FIG. 5B, and serves ascontainment vessel during the extrusion process. A first liquid feedport 76 is disposed in zone 2, a second liquid feed port 78 is disposedin zone 3, and a third liquid feed port 80 is disposed in zone 4. A vent82 is included in zone 1 for cooling and decreasing the liquid, such aswater, content of the mixture prior to exiting the second extruder. Anoptional vent stuffer, commercially available from APV Baker, can beemployed to prevent the aqueous polymer melt composition from exitingthrough the vent 82. The flow of the aqueous polymer melt compositionthrough the barrel 74 is from zone 2 exiting the barrel 74 at zone 5.

A screw and mixing element configuration for the second extruderconsists of twin lead screws (TLS) (designated A, E, F), paddles(designated C), and single lead screws (SLS) (designated G) installed inseries as illustrated in Table 3 below.

TABLE 3 Total Length Length Element Zone Ratio Element Pitch Ratio TypePurpose 1 0.25 Paddle 0 0.25 C Mixing 1 1.75 TLS 2 1.5 E Vent Location 23.25 TLS 2 1.5 E Conveying 2 4.75 TLS 3 1.5 F Feed Inlet Location 3 6.25TLS 3 1.5 F Conveying 3 7.75 TLS 3 1.5 F Conveying 4 9.25 TLS 2 1.5 EConveying 4 10.25 TLS 1 1 A Conveying 4 11.25 TLS 1 1 A Conveying 411.38 Paddle 0 0.125 C Mixing 4 11.50 Paddle 0 0.125 C Mixing 5 11.63Paddle 0 0.125 C Mixing 5 11.75 Paddle 0 0.125 C Mixing 5 12.75 SLS 0.51 G Conveying 5 13.75 SLS 0.5 1 G Conveying

The aqueous polymer melt composition comprising the melt processedhydroxyl polymer and fast wetting surfactant coming from the firstextruder is fed into the second extruder at a point about 5 L/D down thebarrel, liquid feed port 76 (zone 2). A vent 82 open to atmosphericpressure is situated at about 1.5 L/D down the barrel 74 (zone 1). Somewater vapor escapes from the aqueous polymer melt composition and exitsthrough the vent 82. Water, an external plasticizer, and a crosslinkingfacilitator, such as ammonium chloride, may be added at the liquid feedport 78 (zone 3). A non-hydroxyl polymer, such as polyacrylamide, may beadded at liquid feed port 80 (zone 4). Additional additives such asother surfactants, other non-hydroxyl polymers, other salts and/or acidsmay be added at various feed ports along the length of the barrel 74.The aqueous polymer melt composition is then conveyed through theextruder to the end of the barrel 74 (zone 5).

At least a portion of the aqueous polymer melt composition is thendumped and another part (400 g) is fed into a Mahr (Charlotte, N.C.)gear pump and pumped into a SMX style static mixer (Koch-Glitsch,Woodridge, Ill.). The static mixer is used to combine additionaladditives such as crosslinking agents, for example an imidazolidinone,crosslinking facilitators, such as ammonium chloride, externalplasticizers, such as water, with the aqueous polymer melt compositioncomprising the melt processed hydroxyl polymer and fast wettingsurfactant. The additives are pumped into the static mixer via PREP 100HPLC pumps (Chrom Tech, Apple Valley Minn.). These pumps provide highpressure, low volume addition capability. The aqueous polymer meltcomposition of the present invention is now ready to be processed by apolymer processing operation.

b. Polymer Processing

“Polymer processing” as used herein means any operation and/or processby which a polymeric structure comprising a processed hydroxyl polymeris formed from an aqueous polymer melt composition comprising a meltprocessed hydroxyl polymer. Non-limiting examples of polymer processingoperations include extrusion, molding and/or fiber spinning. Extrusionand molding (either casting or blown), typically produce films, sheetsand various profile extrusions. Molding may include injection molding,blown molding and/or compression molding. Fiber spinning may includespunbonding, melt blowing, rotary spinning, continuous filamentproducing and/or tow fiber producing.

A “processed hydroxyl polymer” as used herein means any hydroxyl polymerthat has undergone a melt processing operation and a subsequent polymerprocessing operation.

c. Polymeric Structure

The aqueous polymer melt composition can be subjected to one or morepolymer processing operations such that the polymer melt composition isprocessed into a polymeric structure comprising the hydroxyl polymer anda crosslinking system according to the present invention.

“Polymeric structure” as used herein means any physical structure formedas a result of processing an aqueous polymer melt composition inaccordance with the present invention. Non-limiting examples ofpolymeric structures in accordance with the present invention includefibrous elements (such as filaments and/or fibers), films and/or foams.

A crosslinking system via a crosslinking agent and optionally acrosslinking facilitator may crosslink the processed hydroxyl polymerstogether to produce the polymeric structure of the present invention,with or without being subjected to a curing step. In other words, thecrosslinking system in accordance with the present invention acceptablycrosslinks the processed hydroxyl polymers of a processed polymer meltcomposition together via the crosslinking agent to form an integralpolymeric structure, such as a fibrous element. The crosslinking agentcan function as a “building block” for the polymeric structure. In oneexample, without the crosslinking agent, no polymeric structure inaccordance with the present invention could be formed.

Polymeric structures of the present invention do not include coatingsand/or other surface treatments that are applied to a pre-existing form,such as a coating on a fibrous element, film or foam. However, in oneexample of the present invention, a polymeric structure, such as afibrous element, in accordance with the present invention may be coatedand/or surface treated with a crosslinking system of the presentinvention.

In one example, the polymeric structure produced via a polymerprocessing operation may be cured at a curing temperature of from about110° C. to about 215° C. and/or from about 110° C. to about 200° C.and/or from about 120° C. to about 195° C. and/or from about 130° C. toabout 185° C. for a time period of from about 0.01 and/or 1 and/or 5and/or 15 seconds to about 60 minutes and/or from about 20 seconds toabout 45 minutes and/or from about 30 seconds to about 30 minutes.Alternative curing methods may include radiation methods such as UV,e-beam, IR and other temperature-raising methods.

Further, the polymeric structure may also be cured at room temperaturefor days, either after curing at above room temperature or instead ofcuring at above room temperature.

The polymeric structure may exhibit an initial total wet tensile, asmeasured by the Initial Total Wet Tensile Test Method described herein,of at least about 1.18 g/cm (3 g/in) and/or at least about 1.57 g/cm (4g/in) and/or at least about 1.97 g/cm (5 g/in) to about 23.62 g/cm (60g/in) and/or to about 21.65 g/cm (55 g/in) and/or to about 19.69 g/cm(50 g/in).

The polymeric structures of the present invention may include melt spunfibers and/or spunbond fibers, staple fibers, hollow fibers, shapedfibers, such as multi-lobal fibers and multicomponent fibers, especiallybicomponent fibers. The multicomponent fibers, especially bicomponentfibers, may be in a side-by-side, sheath-core, segmented pie, ribbon,islands-in-the-sea configuration, or any combination thereof. The sheathmay be continuous or non-continuous around the core. The ratio of theweight of the sheath to the core can be from about 5:95 to about 95:5.The fibers of the present invention may have different geometries thatinclude round, elliptical, star shaped, rectangular, and other variouseccentricities.

One or more polymeric structures of the present invention may beincorporated into a multi-polymeric structure product, such as a fibrousstructure and/or web, if the polymeric structures are in the form offibers. Such a multi-polymeric structure product may ultimately beincorporated into a commercial product, such as a single- or multi-plysanitary tissue product, such as facial tissue, bath tissue, papertowels and/or wipes, feminine care products, diapers, writing papers,cores, such as tissue cores, and other types of paper products.

Non-limiting examples of processes for preparing polymeric structures inaccordance with the present invention follow.

i) Fibrous Element Formation

An aqueous polymer melt composition comprising a melt processed hydroxylpolymer and a fast wetting surfactant is prepared according to theSynthesis of an Aqueous Polymer Melt Composition described above. Asshown in FIG. 6 , the aqueous polymer melt composition may be processedinto a fibrous element. The aqueous polymer melt composition present inan extruder 102 is pumped to a die 104 using pump 103, such as aZenith®, type PEP II, having a capacity of 10 cubic centimeters perrevolution (cc/rev), manufactured by Parker Hannifin Corporation, ZenithPumps division, of Sanford, N.C., USA. The aqueous polymer meltcomposition's flow to die 104 is controlled by adjusting the number ofrevolutions per minute (rpm) of the pump 103. Pipes connecting theextruder 102, the pump 103, the die 104, and optionally a mixer 116 areelectrically heated and thermostatically controlled to 65° C.

The die 104 has several rows of circular extrusion nozzles 200 spacedfrom one another at a pitch P (FIG. 7 ) of about 2.489 millimeters(about 0.098 inches). The nozzles are arranged in a staggered grid witha spacing of 2.489 millimeters (about 0.098 inches) within rows and aspacing of 2.159 millimeters (about 0.085 inches) between rows. Thenozzles 200 have individual inner diameters D2 of about 0.254millimeters (about 0.010 inches) and individual outside diameters (D1)of about 0.813 millimeters (about 0.032 inches). Each individual nozzle200 is encircled by an annular orifice 250 formed in a plate 260 (FIGS.7 and 8 ) having a thickness of about 1.9 millimeters (about 0.075inches). A pattern of a plurality of the orifices 250 in the plate 260correspond to a pattern of extrusion nozzles 200. Once the orifice plateis combined with the dies, the resulting area for airflow is about 36percent. The plate 260 is fixed so that the embryonic filaments 110being extruded through the nozzles 200 are surrounded and attenuated bygenerally cylindrical, humidified air streams supplied through theorifices 250. The nozzles can extend to a distance from about 1.5 mm toabout 4 mm, and more specifically from about 2 mm to about 3 mm, beyonda surface 261 of the plate 260 (FIG. 7 ). As shown in FIG. 9 , aplurality of boundary-air orifices 300, is formed by plugging nozzles oftwo outside rows on each side of the plurality of nozzles, as viewed inplane, so that each of the boundary-layer orifice comprised a annularaperture 250 described herein above. Additionally, every other row andevery other column of the remaining capillary nozzles are blocked,increasing the spacing between active capillary nozzles

As shown in FIG. 6 , attenuation air can be provided by heatingcompressed air from a source 106 by an electrical-resistance heater 108,for example, a heater manufactured by Chromalox, Division of EmersonElectric, of Pittsburgh, Pa., USA. An appropriate quantity of steam 105at an absolute pressure of from about 240 to about 420 kiloPascals(kPa), controlled by a globe valve (not shown), is added to saturate ornearly saturate the heated air at the conditions in the electricallyheated, thermostatically controlled delivery pipe 115. Condensate isremoved in an electrically heated, thermostatically controlled,separator 107. The attenuating air has an absolute pressure from about130 kPa to about 310 kPa, measured in the pipe 115. The filaments 110being extruded have a moisture content of from about 20% and/or fromabout 25% to about 50% and/or to about 55% by weight. The filaments 110are dried by a drying air stream 109 having a temperature from about149° C. (about 300° F.) to about 315° C. (about 600° F.) by anelectrical resistance heater (not shown) supplied through drying nozzles112 and discharged at an angle generally perpendicular relative to thegeneral orientation of the embryonic fibers being extruded. Thefilaments 110 are dried from about 45% moisture content to about 15%moisture content (i.e., from a consistency of about 55% to a consistencyof about 85%) and are collected on a collection device 111, such as, forexample, a movable foraminous belt.

The process parameters are as follows in Table 4.

TABLE 4 Sample Units Attenuation Air Flow Rate G/min 9000 AttenuationAir Temperature ° C. 65 Attenuation Steam Flow Rate G/min 1800Attenuation Steam Gage Pressure kPa 213 Attenuation Gage Pressure inDelivery kPa 14 Pipe Attenuation Exit Temperature ° C. 65 Solution PumpSpeed Revs/min 12 Solution Flow G/min/hole 0.18 Drying Air Flow Rateg/min 17000 Air Duct Type Slots Air Duct Dimensions mm 356 × 127Velocity via Pitot-Static Tube M/s 65 Drying Air Temperature at Heater °C. 260 Dry Duct Position from Die mm 80 Drying Duct Angle Relative toFibers degrees 0 Drying Duct to Drying Duct Spacing mm 205 Die toForming Box distance Mm 610 Forming Box Machine direction Length Mm 635Forming Box Cross Direction Width Mm 380 Forming Box Flowrate g/min41000

ii) Foam Formation

The aqueous polymer melt composition for foam formation may be preparedsimilarly as for fibrous element formation except that the added watercontent may be less, typically from about 10-21% of the hydroxyl polymerweight. With less water to plasticize the hydroxyl polymer, highertemperatures are needed in extruder zones 5-8 (FIG. 4A), typically fromabout 150-250° C. Also with less water available, it may be necessary toadd the crosslinking system, especially the crosslinking agent, with thewater in zone 1. In order to avoid premature crosslinking in theextruder, the aqueous polymer melt composition pH should be between 7and 8, achievable by using a crosslinking facilitator e.g., ammoniumsalt. A die is placed at the location where the extruded materialemerges and is typically held at about 160-210° C. Modified high amylosestarches (for example greater than 50% and/or greater than 75% and/orgreater than 90% by weight of the starch of amylose) granulated toparticle sizes ranging from about 400-1500 microns may be used in thepresent invention. It may also be advantageous to add a nucleating agentsuch as microtalc or alkali metal or alkaline earth metal salt such assodium sulfate or sodium chloride in an amount of about 1-8% of thestarch weight. The foam may be shaped into various forms.

iii) Film Formation

The aqueous polymer melt composition for film formation may be preparedsimilarly as for foam formation except that the added water content maybe less, typically 3-15% of the hydroxyl polymer weight and a polyolexternal plasticizer such as glycerol is included at about 10-30% of thehydroxyl polymer weight. As with foam formation, zones 5-7 (FIG. 4A) areheld at about 160-210° C., however, the slit die temperature is lowerbetween 60-120° C. As with foam formation, the crosslinking system,especially the crosslinking agent, may be added along with the water inzone 1 and the aqueous polymer melt composition pH may be between about7-8 achievable by using a crosslinking facilitator e.g., ammonium salt.

Non-Limiting Example of Fibrous Structure of Present Invention

The materials used in the Examples set forth below are as follows:

CPI 050820-156 is an acid-thinned, dent corn starch with a weightaverage molecular weight of 2,000,000 g/mol supplied by Corn ProductsInternational, Westchester, Ill.

Hyperfloc NF301, a nonionic polyacrylamide (PAAM) has a weight averagemolecular weight between 5,000,000 and 6,000,000 g/mol, is supplied byHychem, Inc., Tampa, Fla. Hyperfloc NF221, a nonionic PAAM has a weightaverage molecular weight between 4,000,000 and 5,000,000 g/mol, and isalso supplied by Hychem, Inc.

Aerosol MA-80-PG is an anionic sodium dihexyl sulfosuccinate surfactantsupplied by Cytec Industries, Inc., Woodland Park, N.J.

Example 1

The PAAM solution is prepared by dissolving dry Hyperfloc NF301 in waterto a final concentration of 2.2 wt %. To ensure complete dissolution,the polymer is dissolved under high shear conditions using a high speedmixer. The resulting Hyperfloc NF301 solution has a weight averagemolecular weight of 4,000,000 g/mol. It should be noted that a higherpolyacrylamide molecular weight may be obtained by dissolving the drypolymer at dilute concentration and gentle stirring. However, a dilutepolymer solution would not be useful for the present example. At 25° C.the solution has a shear viscosity approximately 100 Pa*s, and anextensional viscosity of approximately 1000 Pa*s at a Hencky strain of7.

The 2.2% Hyperfloc NF301 solution is delivered to zone one of a 40:1 APVBaker twin-screw extruder with eight temperature zones. There, it ismelt processed with CPI 050820-156 starch, ammonium chloride, AerosolMA-80-PG surfactant, and water. The melt composition reaches a peaktemperature of 170 to 175° C. in the cook extruder. The composition inthe extruder is 42% water where the make-up of solids is 97.2% CPI050820-156, 1.5% Aerosol MA-80-PG, 0.8% Hyperfloc NF301 polyacrylamide,and 0.5% ammonium chloride. This mixture is then conveyed down thebarrel through zones 2 through 8 and cooked into a melt-processedhydroxyl polymer composition. From the extruder, the melt is fed to aMahr gear pump, and then delivered to a second extruder. The secondextruder is a 13:1 APV Baker twin screw, which serves to cool the meltby venting a stream to atmospheric pressure. The second extruder alsoserves as a location for additives to the hydroxyl polymer melt.Particularly, a second stream of 2.2% Hyperfloc NF301 polyacrylamide isintroduced at a level of 0.2% on a solids basis. This raises the totalHyperfloc NF301 level to 1.0% of the solids. The material that is notvented is conveyed down the extruder to a second Mahr melt pump. Fromhere, the hydroxyl polymer melt is delivered to a series of staticmixers where a cross-linker, activator, and water are added. The meltcomposition at this point in the process is 50-55% total solids. On asolids basis the melt is comprised of 90.5% CPI 050820-156 starch, 5%cross-linker, 2% ammonium chloride, 1.5% surfactant, and 1.0% HyperflocNF301 PAAM. From the static mixers the composition is delivered to amelt blowing die via a melt pump.

The resulting attenuated fibers have diameters ranging from 1 to 10microns, and contain polyacrylamide with a weight average molecularweight of 1,300,000 to 2,000,000 g/mol, and MWD of greater than 1.3. Theentanglement concentration of PAAM is roughly 0.70% and 0.45% for a1,300,000 g/mol and 2,000,000 g/mol polyacrylamide respectively. Thus,the composition of Hyperfloc NF301 in the fiber is anywhere from 1.4 to2.2 times its entanglement concentration. The resulting fibrousstructure exhibits a basis weight of 18 g/m² and a Fail Total EnergyAbsorption of 55.

Comparative Example 1

A comparative hydroxyl polymer melt is prepared according to Example 1except a lower weight average molecular weight PAAM is added to the cookextruder. The PAAM solution is prepared by dissolving dry HyperflocNF221 in water to a final concentration of 3.5 wt %. To ensure completedissolution, the polymer is dissolved under high shear conditions usinga high speed mixer. The resulting Hyperfloc NF221 solution has a weightaverage molecular weight of 3,000,000 g/mol. It should be noted that ahigher polyacrylamide molecular weight may be obtained by dissolving thedry polymer at dilute concentration and gentle stirring. However, adilute polymer solution would not be useful for the present example. At25° C. the solution has a shear viscosity less than 100 Pa*s, and anextensional viscosity of approximately 1000 Pa*s at a Hencky strain of7. The Hyperfloc NF221 solution is mixed with starch in a twin-screwextruder to form a hydroxyl polymer melt according to Example 1. Fromhere, the melt composition has Hyperfloc NF301 added in the flashextruder, and cross-linker and activator added in the static mixers asdescribed in Example 1. The resulting melt composition is 50-55% totalsolids. On a solids basis the melt is comprised of 91.1% CPI 050820-156starch, 5% cross-linker, 2% ammonium chloride, 1.5% surfactant, 0.8%Hyperfloc NF221 PAAM, and 0.2% Hyperfloc NF301 PAAM. From the staticmixers the composition is delivered to a melt blowing die via a meltpump. The resulting attenuated fibers have diameters ranging from 1 to10 microns, and contain polyacrylamide with a weight average molecularweight of 1,300,000 to 2,000,000 g/mol and a MWD greater than 1.3, whichis the same as Example 1. The concentration of polyacrylamide in thefiber is above its entanglement threshold, 1.4 to 2.2 times higher thanthe entanglement concentration. The resulting fibrous structure exhibitsa basis weight of 18 g/m² and a Fail Total Energy Absorption of 55. Thefail properties are the same as Example 1 because the PAAM Mw and MWD inthe fiber are the same.

The twin-screw cook extruder (extruder 1) provides a high shear stressenvironment that provides mixing of the individual melt components intoa homogeneous hydroxyl polymer melt composition. Particularly, extruder1 imparts very good mixing and interpenetration of the starch moleculesand Hyperfloc NF301 polyacrylamide chains. The resulting hydroxylpolymer melt contains entangled polyacrylamide chains. However, the highshear stress conditions in the cook extruder also cause mechanicaldegradation of high molecular weight polymers. For example, even thoughHyperfloc NF301 (M_(w)=4,000,000 g/mol) and the Hyperfloc NF221(M_(w)=3,000,000 g/mol) have different molecular weights in solution,they are both mechanically degraded to the same final weight averagemolecular weight in extruder 1. This is why the polyacrylamide molecularweight and distribution in Example 1 and 2 are identical. Unlike thehigh shear stress in extruder 1, the second extruder imposes low shearstress on the composition due to the melt's low viscosity. After thecomposition exits the extruder 1 it is fully cooked and homogenous andpossesses a low melt viscosity. Thus, shear degradation of the HyperflocNF301 at the second extruder is mitigated compared to extruder 1.

Comparative Example 2

A comparative hydroxyl polymer melt is prepared as described in Example1 except the Hyperfloc NF301 is added in the first extruder, and none inthe venting extruder. A higher concentration of Hyperfloc NF301 is addedto the first extruder such that the final composition is identical toExample 1. The hydroxyl polymer melt composition in the first extruderis 42% water where the make-up of solids is 97.4% CPI 050820-156, 1.5%Aerosol MA-80-PG, 1.0% Hyperfloc NF301 polyacrylamide, and 0.5% ammoniumchloride. After addition of the cross linker, the final composition ofthe melt is the same as Example 1, and is spun into filaments. Theresulting filaments contain polyacrylamide with a measure weight averagemolecular weight of 1,000,000 to 1,300,000 g/mol and a MWD 1.2 to 1.3.The resulting fibrous structure exhibits a basis weight of 18 g/m² and aFail Total Energy Absorption of 35. The tensile properties are lowerthan Examples 1 and 2 because the fiber contains a lower molecularweight PAAM. The molecular weight and MWD are both lower compared toExamples 1 and 2 because no polyacrylamide is added at the secondextruder, and the Hyperfloc NF301 added at the cook extruder issignificantly shear degraded. The concentration of polyacrylamide in thefiber is only slightly above its entanglement threshold—1.1 to 1.4 timeshigher than the entanglement concentration.

Comparative Example 3

A comparative hydroxyl polymer melt is prepared as described inComparative Example 2 except the Hyperfloc NF301 PAAM is added at thesecond extruder instead of the first. The composition in the firstextruder is 42% water where the make-up of solids is 98.0% CPI050820-156, 1.5% Aerosol MA-80-PG, and 0.5% ammonium chloride. Thismixture is then fed to the second extruder where Hyperfloc NF301 isadded at a level of 0.4% on a solids basis. The hydroxyl polymer melt isthen delivered to a series of static mixers where a cross-linker,activator, and water are added as described in Example 1. The meltcomposition at this point in the process is 50-55% total solids. On asolids basis the melt is comprised of 91.1% CPI 050820-156 starch, 5%cross-linker, 2% ammonium chloride, 1.5% surfactant, and 0.4% HyperflocNF301 PAAM. From the static mixers the composition is delivered to amelt blowing die via a melt pump. The resulting attenuated fibers havediameters ranging from 1 to 10 microns, and contain polyacrylamide witha weight average molecular weight of 2,300,000 g/mol and MWD of 1.2 to1.3. The resulting fibrous structure exhibits a basis weight of 18 g/m²and a Fail Total Energy Absorption of 30. The tensile properties arelower than Examples 1 and 2 because the polyacrylamide is not wellmixed/intimately entangled with the starch.

The molecular weight of polyacrylamide in the fiber is higher thanExamples 1 through 3 because none of the Hyperfloc NF301 is added to thecook extruder which shear degrades the polymer. However, the tensileproperties of the resulting fibers are still lower than Examples 1 and 2because there is not sufficient mixing between the starch molecules andpolyacrylamide chains to form effective entanglements.

Test Methods of the Present Invention

Unless otherwise specified, all tests described herein including thosedescribed under the Definitions section and the following test methodsare conducted on samples that have been conditioned in a conditionedroom at a temperature of 23° C.±1.0° C. and a relative humidity of50%±2% for a minimum of 12 hours prior to the test. All plastic andpaper board packaging articles of manufacture, if any, must be carefullyremoved from the samples prior to testing. The samples tested are“usable units.” “Usable units” as used herein means sheets, flats fromroll stock, pre-converted flats, and/or single or multi-ply products.Except where noted all tests are conducted in such conditioned room, alltests are conducted under the same environmental conditions and in suchconditioned room. Discard any damaged product. Do not test samples thathave defects such as wrinkles, tears, holes, and like. All instrumentsare calibrated according to manufacturer's specifications.

Shear Viscosity of a Polymer Melt Composition Measurement Test Method

The shear viscosity of a polymer melt composition comprising acrosslinking system is measured using a capillary rheometer, GoettfertRheograph 6000, manufactured by Goettfert USA of Rock Hill S.C., USA.The measurements are conducted using a capillary die having a diameter Dof 1.0 mm and a length L of 30 mm (i.e., L/D=30). The die is attached tothe lower end of the rheometer's 20 mm barrel, which is held at a dietest temperature of 75° C. A preheated to die test temperature, 60 gsample of the polymer melt composition is loaded into the barrel sectionof the rheometer. Rid the sample of any entrapped air. Push the samplefrom the barrel through the capillary die at a set of chosen rates1,000-10,000 seconds⁻¹. An apparent shear viscosity can be calculatedwith the rheometer's software from the pressure drop the sampleexperiences as it goes from the barrel through the capillary die and theflow rate of the sample through the capillary die. The log(apparentshear viscosity) can be plotted against log (shear rate) and the plotcan be fitted by the power law, according to the formula η=Kγ^(n-1),wherein K is the material's viscosity constant, n is the material'sthinning index and γ is the shear rate. The reported apparent shearviscosity of the composition herein is calculated from an interpolationto a shear rate of 3,000 sec⁻¹ using the power law relation.

Basis Weight Test Method

Basis weight of a fibrous structure is measured on stacks of twelveusable units using a top loading analytical balance with a resolution of±0.001 g. The balance is protected from air drafts and otherdisturbances using a draft shield. A precision cutting die, measuring3.500 in ±0.0035 in by 3.500 in ±0.0035 in is used to prepare allsamples.

With a precision cutting die, cut the samples into squares. Combine thecut squares to form a stack twelve samples thick. Measure the mass ofthe sample stack and record the result to the nearest 0.001 g.

The Basis Weight is calculated in lbs/3000 ft² or g/m² as follows:Basis Weight=(Mass of stack)/[(Area of 1 square in stack)×(No. ofsquares in stack)]For example,Basis Weight (lbs/3000 ft²)=[[Mass of stack (g)/453.6 (g/lbs)]/[12.25(in²)/144 (in²/ft²)×12]]×3000or,Basis Weight (g/m²)=Mass of stack (g)/[79.032 (cm²)/10,000 (cm²/m²)×12]Report result to the nearest 0.1 lbs/3000 ft² or 0.1 g/m². Sampledimensions can be changed or varied using a similar precision cutter asmentioned above, so as at least 100 square inches of sample area instack.Initial Total Wet Tensile Test Method

Cut tensile strips precisely in the direction indicated; four to themachine direction (MD) and four to the cross direction (CD). Cut thesample strips 4 in. (101.6 mm) long and exactly 1 in. (25.4 mm) wideusing an Alpha Precision Sample Cutter Model 240-7A (pneumatic):Thwing-Albert Instrument Co and an appropriate die.

An electronic tensile tester (Thwing-Albert EJA Vantage Tester,Thwing-Albert Instrument Co., 10960 Dutton Rd., Philadelphia, Pa.,19154) is used and operated at a crosshead speed of 4.0 inch (about10.16 cm) per minute, using a strip of a fibrous structure of 1 inchwide and a length of about 4 inches long. The gauge length is set to 1inch. The strip is inserted into the jaws with the 1 inch wide sectionin the clamps, verifying that the sample is hanging straight into thebottom jaw. The sample is then pre-loaded with 20-50 g/in of pre-loadforce. This tension is applied to the web to define the adjusted gaugelength, and, by definition is the zero strain point. The sample is thenwet thoroughly with water using a syringe to gently apply the water onthe uppermost portion of the web sample inside the jaws. Crossheadmovement is then initiated within 3-8 seconds after initial watercontact. The initial result of the test is an array of data in the formload (grams force) versus crosshead displacement (centimeters fromstarting point).

The sample is tested in two orientations, referred to here as MD(machine direction, i.e., in the same direction as the continuouslywound reel and forming fabric) and CD (cross-machine direction, i.e.,90° from MD). The MD and CD wet tensile strengths are determined usingthe above equipment and calculations in the following manner:Initial Total Wet Tensile=ITWT (g_(f)/inch)=Peak Load_(MD) (g_(f))/2(inch_(width))+Peak Load_(CD) (g_(f))/2 (inch_(width))

The Initial Total Wet Tensile value is then normalized for the basisweight of the strip from which it was tested. The normalized basisweight used is 24 g/m², and is calculated as follows:Normalized {ITWT}={ITWT}*24 (g/m²)/Basis Weight of Strip (g/m²)

In one example, the initial total wet tensile of a polymeric structure,such as a fibrous structure, of the present invention is at least 1.18g/cm (3 g/in) and/or at least 1.57 g/cm (4 g/in) and/or at least 1.97g/cm (5 g/in) then the crosslinking system is acceptable. The initialtotal wet tensile may be less than or equal to about 23.62 g/cm (60g/in) and/or less than or equal to about 21.65 g/cm (55 g/in) and/orless than or equal to about 19.69 g/cm (50 g/in).

Dry Tensile Strength Test Method

Elongation (Stretch), Tensile Strength, TEA and Tangent Modulus aremeasured on a constant rate of extension tensile tester with computerinterface (a suitable instrument is the EJA Vantage from theThwing-Albert Instrument Co. Wet Berlin, N.J.) using a load cell forwhich the forces measured are within 10% to 90% of the limit of the loadcell. Both the movable (upper) and stationary (lower) pneumatic jaws arefitted with smooth stainless steel faced grips, with a design suitablefor testing 1 inch wide sheet material (Thwing-Albert item #733GC). Anair pressure of about 60 psi is supplied to the jaws.

Eight usable units of fibrous structures are divided into two stacks offour usable units each. The usable units in each stack are consistentlyoriented with respect to machine direction (MD) and cross direction(CD). One of the stacks is designated for testing in the MD and theother for CD. Using a one inch precision cutter (Thwing-Albert JDC-1-10,or similar) take a CD stack and cut one, 1.00 in ±0.01 in wide by 3-4 inlong stack of strips (long dimension in CD). In like fashion cut theremaining stack in the MD (strip's long dimension in MD), to give atotal of 8 specimens, four CD and four MD strips. Each strip to betested is one usable unit thick, and will be treated as a unitaryspecimen for testing.

Program the tensile tester to perform an extension test, collectingforce and extension data at an acquisition rate of 20 Hz as thecrosshead raises at a rate of 2.00 in/min (5.08 cm/min) until thespecimen breaks. The break sensitivity is set to 80%, i.e., the test isterminated when the measured force drops to 20% of the maximum peakforce, after which the crosshead is returned to its original position.

Set the gage length to 1.00 inch. Zero the crosshead and load cell.Insert the specimen into the upper and lower open grips such that atleast 0.5 inches of specimen length is contained in each grip. Alignspecimen vertically within the upper and lower jaws, then close theupper grip. Verify specimen is aligned, then close lower grip. Thespecimen should be fairly straight between grips, with no more than 5.0g of force on the load cell. Add a pre-tension force of 3 g. Thistension is applied to the specimen to define the adjusted gauge length,and, by definition is the zero strain point. Start the tensile testerand data collection. Repeat testing in like fashion for all four CD andfour MD specimens. Program the software to calculate the following fromthe constructed force (g) verses extension (in) curve.

Eight samples are run on the Tensile Tester (four to the MD and four tothe CD) and average of the respective dry total tensile, dry peak TEAand dry Fail Stretch is reported as the Dry Total Tensile, Dry peak TEAand Dry Fail Stretch. Peak TEA is defined as tensile energy absorbed(area under the load vs. strain tensile curve) from zero strain to peakforce point, with units of g/in. Dry Fail Stretch is defined as thepercentage strain measured after the web is strained past its peak loadpoint, where the force drops to exactly 50% of its peak load force.

The dry peak TEA is then normalized for the basis weight of the stripfrom which it was tested. The normalized basis weight used is 24 g/m²,and is calculated as follows:Normalized {dry peak TEA}={dry peak TEA}*24 (g/m²)/Basis Weight of Strip(g/m²)

The MD and CD dry tensile strengths are determined using the aboveequipment and calculations in the following manner.

Tensile Strength in general is the maximum peak force (g) divided by thespecimen width (1 in), and reported as g/in to the nearest 1 g/in.Average Tensile Strength=sum of tensile loads measures (MD)/(Number oftensile stripes tested (MD)*Number of useable units or plys per tensilestripe)

This calculation is repeated for cross direction testing.Dry Total Tensile=Average MD tensile strength+Average CD tensilestrength

The Dry Tensile value is then normalized for the basis weight of thestrip from which it was tested. The normalized basis weight used is 24g/m², and is calculated as follows:Normalized {DTT}={DTT}*24 (g/m²)/Basis Weight of Strip (g/m²)

The various values are calculated for the four CD specimens and the fourMD specimens. Calculate an average for each parameter separately for theCD and MD specimens.

Water Content of a Polymer Melt Composition Test Method

A water content of a polymer melt composition is determined as follows.A weighed sample of a polymer melt composition (4-10 g) is placed in a120° C. convection oven for 8 hours. The sample is reweighed afterremoving from the oven. The % weight loss is recorded as the watercontent of the melt.

Polymer Melt Composition pH Test Method

A polymer melt composition pH is determined by adding 25 mL of thepolymer melt composition to 100 mL of deionized water, stirring with aspatula for 1 min and measuring the pH.

Weight Average Molecular Weight and Molecular Weight Distribution TestMethod

The weight average molecular weight and the molecular weightdistribution (MWD) are determined by Gel Permeation Chromatography (GPC)using a mixed bed column. The column (Waters linear ultrahydrogel,length/ID: 300×7 8 mm) is calibrated with a narrow molecular weightdistribution polysaccharide, 43,700 g/mol from Polymer Laboratories).The calibration standards are prepared by dissolving 0.024 g ofpolysaccharide and 6.55 g of the mobile phase in a scintillation vial ata concentration of 4 mg/ml. The solution sits undisturbed overnight.Then it is gently swirled and filtered with a 5 micron nylon syringefilter into an auto-sampler vial.

The sample for determination of a material, such as a non-hydroxylpolymer, for example polyacrylamide, weight average molecular weight andMWD is prepared by acid-hydrolyzing the fibrous elements within afibrous structure. 1 g of a fibrous structure comprising fibrouselements is placed into a 30 mL pressure tube with 14 g of 0.1N HCl andheated to 130° C. for 1 hour. After the sample is removed from the ovenand cooled, the solution is neutralized to pH 7 with sodium bicarbonate,and passed through a 5 micron filter. The acid hydrolysis reactionbreaks up the cross-linked and uncross-linked starch molecules to verylow molecular weight, while retaining the material, such as thenon-hydroxyl polymer, for example polyacrylamide, molecular weight sincea carbon-carbon polymer backbone is not susceptible to reaction with theacid.

The filtered sample solution is taken up by the auto-sampler to flushout previous test materials in a 100 μL injection loop and inject thepresent test material into the column. The column is held at 50° C.using a Waters TCM column heater. The sample eluded from the column ismeasured against the mobile phase background by a differentialrefractive index detector (Wyatt Optilab DSP interferometricrefractometer) and a multi-angle later light scattering detector (WyattDEAWN EOS 18 angle laser light detector) held at 50° C. The mobile phaseis water with 0.03M potassium phosphate, 0.2M sodium nitrate, and 0.02%sodium azide. The flowrate is set at 0.8 mL/min with a run time of 35minutes.

Relative Humidity Test Method

Relative humidity is measured using wet and dry bulb temperaturemeasurements and an associated psychometric chart. Wet bulb temperaturemeasurements are made by placing a cotton sock around the bulb of athermometer. Then the thermometer, covered with the cotton sock, isplaced in hot water until the water temperature is higher than ananticipated wet bulb temperature, more specifically, higher than about82° C. (about 180° F.). The thermometer is placed in the attenuating airstream, at about 3 millimeters (about ⅛ inch) from the extrusion nozzletips. The temperature will initially drop as the water evaporates fromthe sock. The temperature will plateau at the wet bulb temperature andthen will begin to climb once the sock loses its remaining water. Theplateau temperature is the wet bulb temperature. If the temperature doesnot decrease, then the water is heated to a higher temperature. The drybulb temperature is measured using a 1.6 mm diameter J-type thermocoupleplaced at about 3 mm downstream from the extrusion nozzle tip.

Based on a standard atmospheric psychometric chart or an Excel plug-in,such as for example, “MoistAirTab” manufactured by ChemicaLogicCorporation, a relative humidity is determined Relative Humidity can beread off the chart, based on the wet and dry bulb temperatures.

Air Velocity Test Method

A standard Pitot tube is used to measure the air velocity. The Pitottube is aimed into the air stream, producing a dynamic pressure readingfrom an associated pressure gauge. The dynamic pressure reading, plus adry bulb temperature reading is used with the standard formulas togenerate an air velocity. A 1.24 mm (0.049 inches) Pitot tube,manufactured by United Sensor Company of Amherst, N.H., USA, isconnected to a hand-held digital differential pressure gauge (manometer)for the velocity measurements.

Average Diameter Test Method

A fibrous structure comprising fibrous elements of appropriate basisweight (approximately 5 to 20 grams/square meter) is cut into arectangular shape, approximately 20 mm by 35 mm. The sample is thencoated using a SEM sputter coater (EMS Inc, Pa., USA) with gold so as tomake the fibers relatively opaque. Typical coating thickness is between50 and 250 nm. The sample is then mounted between two standardmicroscope slides and compressed together using small binder clips. Thesample is imaged using a 10× objective on an Olympus BHS microscope withthe microscope light-collimating lens moved as far from the objectivelens as possible. Images are captured using a Nikon D1 digital camera. AGlass microscope micrometer is used to calibrate the spatial distancesof the images. The approximate resolution of the images is 1 μm/pixel.Images will typically show a distinct bimodal distribution in theintensity histogram corresponding to the fibers and the background.Camera adjustments or different basis weights are used to achieve anacceptable bimodal distribution. Typically 10 images per sample aretaken and the image analysis results averaged.

The images are analyzed in a similar manner to that described by B.Pourdeyhimi, R. and R. Dent in “Measuring fiber diameter distribution innonwovens” (Textile Res. J. 69(4) 233-236, 1999). Digital images areanalyzed by computer using the MATLAB (Version. 6.1) and the MATLABImage Processing Tool Box (Version 3.) The image is first converted intoa grayscale. The image is then binarized into black and white pixelsusing a threshold value that minimizes the intraclass variance of thethresholded black and white pixels. Once the image has been binarized,the image is skeltonized to locate the center of each fiber in theimage. The distance transform of the binarized image is also computed.The scalar product of the skeltonized image and the distance mapprovides an image whose pixel intensity is either zero or the radius ofthe fiber at that location. Pixels within one radius of the junctionbetween two overlapping fibers are not counted if the distance theyrepresent is smaller than the radius of the junction. The remainingpixels are then used to compute a length-weighted histogram of fiberdiameters contained in the image.

Degradation of Fibrous Structure Test Method

Approximately 2 g of a fibrous structure comprised of a fibrouselement-forming polymer, such as starch, and a non-hydroxyl polymer,such as a polyacrylamide, is placed into a 30 mL pressure tube with 14 gof 1N HCl, and heated to 130° C. for 45 minutes. The solution isfiltered through a glass microfiber with 1 m pore size, and neutralizedto pH 7 with sodium bicarbonate. Assuming no loss of the non-hydroxylpolymer, the solution is run through a gel permeation chromatographycolumn using the Weight Average Molecular Weight Method with thefollowing changes:

Samples are injected, without dilution, after being filtered with aWhatman GD/X nylon, 5 μm syringe filter. The column used is a WatersLinear Ultrahydrogel (molecular weight ranges from 100 to 7,000,000g/mol) measuring 7.8×300 mm. The column temperature is 50° C. and theinjection volume is 100 μl. The aqueous mobile phase contains 0.03Mpotassium phosphate, 0.2M sodium nitrate and 0.02% sodium azide. Themobile phase is adjusted to pH7 with sodium hydroxide. Run time is 25minutes.

Determination of Total Free Surfactant in Fibrous Structure Using WaterExtraction/HPLC Test Method

The amount of total free surfactant in a fibrous structure is determinedby placing a 0.5 g sample of the fibrous structure in 10 mL of distilledwater in a glass vial with lid for 18 hours. After the 18 hours, shakevigorously for 1 minute. Next remove a 2-3 mL aliquot of the liquid(“extract”) from the glass vial with a syringe. Place a syringe filter(GHP Acrodisc 25 mm syringe filter with 0.45 μm GHP membrane) on thesyringe and deliver the extract in the syringe to a scintillation vial.Determine the weight of the extract in the scintillation vial. Add anamount of acetonitrile to the extract to make a 70:30acetonitrile:extract mixture. Remove a 1-2 mL aliquot of theacetonitrile:extract mixture with a syringe. Place a syringe filter (GHPAcrodisc 25 mm syringe filter with 0.45 μm GHP membrane) on the syringeand deliver the acetonitrile:extract in the syringe to an HPLC vial.HPLC is run to characterize the extract. Linear regression is used tocalculate the total amount of free surfactant extracted from the fibrousstructure.

HPLC Conditions:

Mobile phase: 0.005M tetrabutylammonium phosphate in 70:30acetonitrile:water.

Column. Waters Bondapak C18 3.9×150 mm

Flow Rate: 0.5 mL

UV detector @ 214 nm

Extraction: 0.5 gm web in 10 mL water or acetone

Wetting Rate Test Method

-   -   1. The syringe and tubing of the DAT Fibro 1100 system are        rinsed with Millipore Water 3 times.    -   2. The syringe is loaded with Millipore 18MΩ water and the air        bubbles are eliminated from the top before inserting into the        instrument.    -   3. The DAT Fibro 1100 is calibrated with the calibration        standard provided by the manufacturer. After calibration the        height, base, volume, and angle should be within target. If not,        make the necessary adjustments following the manufacturer's        instructions.

Calibration Targets Height  0.93 ± 0.02 mm Base  1.99 ± 0.05 mm Volume 1.87 ± 0.05 μL Angle 85.9° ± 1°

-   -   4. From each fibrous structure, strips are cut to obtain 8        measurements for each sample block. The fibrous structures are        handled with clean tweezers. Minimum contact with the measured        surface of the fibrous structure is required.    -   5. The fibrous structures are placed onto the sample block with        double sided tape. The fibrous structures must lay flat on the        sample block with no bending or curling in order to obtain an        accurate measurement.    -   6. The following conditions are used for the Contact Angle        Tester:

Liquid: Millipore Water Steps: 1 References Lines Timeout 0.3 minMinimum height: 7 Mod threshold: 0 # Of Drops 8 Minimum width: 10Cannula Tip: 442 Drop size 10 microliter Capture Offset: 0 Drop bottom:305 Stroke pulse 15 Travel time: 10 Paper Position: 77 Time collected:0.01 sec Pump delay: 2 Batch Mode: Manual 0.02 sec 0.03 sec

-   -   7. When measuring the contact angle it is important that the        drop be applied to the sample surface with as little force and        bouncing as possible. Therefore it may be necessary to adjust        the sample height and tubing in order to assure that the drop is        applied properly and the measurement recorded accurately.    -   8. Once all the data has been collected it is saved as a *.DAT        file which is then opened in the analysis program JMP.    -   9. In JMP the time and angle measurements are plotted, resulting        in an exponential decay curve. This curve fits the first order        rate equation A=A₀e^(−kt) where k is the wetting rate of the        fibrous structure.    -   10. The measurements time and angle values are combined and        plotted.    -   11. The rate equation is then fitted to the points to determine        A₀ and k for the sample set. The standard deviation is also        calculated in JMP. The standard deviation for each value is        defined as the product of the square root of the mean squared        error and the square root of the diagonals of the derivative        cross-products matrix inverse.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

All documents cited in the Detailed Description of the Invention are, inrelevant part, incorporated herein by reference; the citation of anydocument is not to be construed as an admission that it is prior artwith respect to the present invention.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. A non-thermoplastic crosslinked fibrous elementcomprising a blend of a non-thermoplastic, water-soluble hydroxylpolymer, a fast wetting surfactant comprising a sulfosuccinatesurfactant comprising a C₄-C₇ aliphatic chain, and a non-hydroxylpolymer selected from the group consisting of: polyacrylamide and itsderivatives; polyacrylic acid, polymethacrylic acid and their esters;polyethyleneimine; copolymers made from mixtures of the aforementionedpolymers; and mixtures thereof, wherein the non-thermoplasticcrosslinked fibrous element is produced from an aqueous solutioncomprising the non-thermoplastic, water-soluble hydroxyl polymer, thefast wetting surfactant, a crosslinking agent, and the non-hydroxylpolymer and wherein the non-hydroxyl polymer exhibits a weight averagemolecular weight of greater than 1,400,000 g/mol and a polydispersity ofgreater than 1.10 to 1.40, and wherein the non-hydroxyl polymer ispresent in the blend at a concentration greater than its entanglementconcentration (Ce) and wherein the non-thermoplastic crosslinked fibrouselement is cured at a curing temperature of from about 110° C. to about215° C.
 2. The non-thermoplastic crosslinked fibrous element accordingto claim 1 wherein the non-hydroxyl polymer comprises a linear polymer.3. The non-thermoplastic crosslinked fibrous element according to claim1 wherein the non-hydroxyl polymer comprises a long chain branchedpolymer.
 4. The non-thermoplastic crosslinked fibrous element accordingto claim 1 wherein the non-hydroxyl polymer is compatible with thenon-thermoplastic, water-soluble hydroxyl polymer at a concentrationgreater than the non-hydroxyl polymer's entanglement concentrationC_(e).
 5. The non-thermoplastic crosslinked fibrous element according toclaim 1 wherein the non-hydroxyl polymer comprises polyacrylamide. 6.The non-thermoplastic crosslinked fibrous element according to claim 1wherein the non-thermoplastic crosslinked fibrous element comprises fromabout 0.001% to about 10% by weight of the non-thermoplastic crosslinkedfibrous element of the non-hydroxyl polymer.
 7. The non-thermoplasticcrosslinked fibrous element according to claim 1 wherein thenon-thermoplastic, water-soluble hydroxyl polymer comprises apolysaccharide.
 8. The non-thermoplastic crosslinked fibrous elementaccording to claim 7 wherein the polysaccharide is selected from thegroup consisting of: starch, starch derivatives, starch copolymers,chitosan, chitosan derivatives, chitosan copolymers, cellulose,cellulose derivatives, cellulose derivatives, cellulose copolymers,hemicelluloses, hemicelluloses derivatives, hemicelluloses copolymers,and mixtures thereof.
 9. The non-thermoplastic crosslinked fibrouselement according to claim 1 wherein the non-thermoplastic crosslinkedfibrous element comprises a non-thermoplastic crosslinked filament. 10.A fibrous structure comprising a plurality of non-thermoplasticcrosslinked fibrous elements according to claim
 1. 11. A single- ormulti-ply sanitary tissue product comprising a fibrous structureaccording to claim
 10. 12. A method for making a non-thermoplasticcrosslinked fibrous element, the method comprising the steps of: a.polymer processing a polymer melt composition comprising an aqueoussolution comprising a non-thermoplastic, water-soluble hydroxyl polymer,a fast wetting surfactant comprising a sulfosuccinate surfactantcomprising a C₄-C₇ aliphatic chain, a crosslinking agent, and anon-hydroxyl polymer selected from the group consisting of:polyacrylamide and its derivatives; polyacrylic acid, polymethacrylicacid and their esters; polyethyleneimine; copolymers made from mixturesof the aforementioned polymers; and mixtures thereof, wherein thenon-hydroxyl polymer exhibits a weight average molecular weight ofgreater than 1,400,000 g/mol and a polydispersity of greater than 1.10to 1.40 such that a fibrous element is formed; and b. curing the fibrouselement at a curing temperature of from about 110° C. to about 215° C.such that a non-thermoplastic crosslinked fibrous element according toclaim 1 is produced.
 13. The method according to claim 12 wherein thecrosslinking agent is capable of crosslinking the non-thermoplastic,water-soluble hydroxyl polymer.
 14. The method according to claim 12wherein the method further comprises the step of collecting a pluralityof non-thermoplastic crosslinked fibrous elements on a collection deviceto produce a fibrous structure.
 15. A non-thermoplastic crosslinkedfibrous element comprising a blend of a non-thermoplastic, water-solublehydroxyl polymer, a fast wetting surfactant comprising a sulfosuccinatesurfactant comprising a C₄-C₇ aliphatic chain, and a non-hydroxylpolymer selected from the group consisting of: polyacrylamide and itsderivatives; polyacrylic acid, polymethacrylic acid and their esters;polyethyleneimine; copolymers made from mixtures of the aforementionedpolymers, wherein the non-thermoplastic crosslinked fibrous element isproduced from an aqueous solution comprising the non-thermoplastic,water-soluble hydroxyl polymer, the fast wetting surfactant, acrosslinking agent, and the non-hydroxyl polymer and wherein thenon-hydroxyl polymer exhibits a polydispersity of at least 1.32 to 1.40,and wherein the non-hydroxyl polymer is present in the blend at aconcentration greater than its entanglement concentration (Ce) andwherein the non-thermoplastic crosslinked fibrous element is cured at acuring temperature of from about 110° C. to about 215° C.
 16. Thenon-thermoplastic crosslinked fibrous element according to claim 15wherein the non-hydroxyl polymer comprises a polyacrylamide.
 17. Thenon-thermoplastic crosslinked fibrous element according to claim 15wherein the non-hydroxyl polymer comprises a linear polymer.
 18. Thenon-thermoplastic crosslinked fibrous element according to claim 15wherein the non-hydroxyl polymer is compatible with thenon-thermoplastic, water-soluble hydroxyl polymer at a concentrationgreater than the non-hydroxyl polymer's entanglement concentrationC_(e).
 19. The non-thermoplastic crosslinked fibrous element accordingto claim 15 wherein the non-thermoplastic, water-soluble hydroxylpolymer comprises a polysaccharide.